diff --git a/docs/isc-wf-1.md b/docs/isc-wf-1.md
index 9e51966..fb3760e 100644
--- a/docs/isc-wf-1.md
+++ b/docs/isc-wf-1.md
@@ -127,6 +127,10 @@ Let R = the ordered list of rules produced by expanding the ruleset
    added (row 3 covers them — they appear at the end).
 5. The whole expansion (R_kept + O) participates in the enclosing
    stage's single longest-match pass like any other rules.
+6. Placement of O: when the expansion ends with a parallel block, O's
+   rows join that block, so R_kept and O share one longest-match pass
+   (replacement acts on the source-script pass, §4.3). Otherwise O
+   appends after R_kept as stage-level rows.
 
 ### 4.3 Rationale notes (non-normative)
 
diff --git a/libs/thai-latn.isc b/libs/thai-latn.isc
new file mode 100644
index 0000000..f7391df
--- /dev/null
+++ b/libs/thai-latn.isc
@@ -0,0 +1,335 @@
+system "thai-latn" {
+
+ruleset leading_vowel_digraphs {
+  parallel {
+    sub "เก" "ke"
+    sub "เกา" "kao"
+    sub "เข" "khe"
+    sub "เขา" "khao"
+    sub "เฃ" "khe"
+    sub "เฃา" "khao"
+    sub "เค" "khe"
+    sub "เคา" "khao"
+    sub "เฅ" "khe"
+    sub "เฅา" "khao"
+    sub "เฆ" "khe"
+    sub "เฆา" "khao"
+    sub "เง" "nge"
+    sub "เงา" "ngao"
+    sub "เจ" "che"
+    sub "เจา" "chao"
+    sub "เฉ" "che"
+    sub "เฉา" "chao"
+    sub "เช" "che"
+    sub "เชา" "chao"
+    sub "เฌ" "che"
+    sub "เฌา" "chao"
+    sub "เญ" "ye"
+    sub "เญา" "yao"
+    sub "เฎ" "de"
+    sub "เฎา" "dao"
+    sub "เฏ" "te"
+    sub "เฏา" "tao"
+    sub "เฐ" "the"
+    sub "เฐา" "thao"
+    sub "เฑ" "the"
+    sub "เฑา" "thao"
+    sub "เฒ" "the"
+    sub "เฒา" "thao"
+    sub "เณ" "ne"
+    sub "เณา" "nao"
+    sub "เด" "de"
+    sub "เดา" "dao"
+    sub "เต" "te"
+    sub "เตา" "tao"
+    sub "เถ" "the"
+    sub "เถา" "thao"
+    sub "เท" "the"
+    sub "เทา" "thao"
+    sub "เธ" "the"
+    sub "เธา" "thao"
+    sub "เน" "ne"
+    sub "เนา" "nao"
+    sub "เบ" "be"
+    sub "เบา" "bao"
+    sub "เป" "pe"
+    sub "เปา" "pao"
+    sub "เผ" "phe"
+    sub "เผา" "phao"
+    sub "เฝ" "fe"
+    sub "เฝา" "fao"
+    sub "เพ" "phe"
+    sub "เพา" "phao"
+    sub "เฟ" "fe"
+    sub "เฟา" "fao"
+    sub "เภ" "phe"
+    sub "เภา" "phao"
+    sub "เม" "me"
+    sub "เมา" "mao"
+    sub "เย" "ye"
+    sub "เยา" "yao"
+    sub "เร" "re"
+    sub "เรา" "rao"
+    sub "เล" "le"
+    sub "เลา" "lao"
+    sub "เว" "we"
+    sub "เวา" "wao"
+    sub "เศ" "se"
+    sub "เศา" "sao"
+    sub "เษ" "se"
+    sub "เษา" "sao"
+    sub "เส" "se"
+    sub "เสา" "sao"
+    sub "เฬ" "le"
+    sub "เฬา" "lao"
+    sub "เฮ" "he"
+    sub "เฮา" "hao"
+    sub "แก" "kae"
+    sub "แข" "khae"
+    sub "แฃ" "khae"
+    sub "แค" "khae"
+    sub "แฅ" "khae"
+    sub "แฆ" "khae"
+    sub "แง" "ngae"
+    sub "แจ" "chae"
+    sub "แฉ" "chae"
+    sub "แช" "chae"
+    sub "แฌ" "chae"
+    sub "แญ" "yae"
+    sub "แฎ" "dae"
+    sub "แฏ" "tae"
+    sub "แฐ" "thae"
+    sub "แฑ" "thae"
+    sub "แฒ" "thae"
+    sub "แณ" "nae"
+    sub "แด" "dae"
+    sub "แต" "tae"
+    sub "แถ" "thae"
+    sub "แท" "thae"
+    sub "แธ" "thae"
+    sub "แน" "nae"
+    sub "แบ" "bae"
+    sub "แป" "pae"
+    sub "แผ" "phae"
+    sub "แฝ" "fae"
+    sub "แพ" "phae"
+    sub "แฟ" "fae"
+    sub "แภ" "phae"
+    sub "แม" "mae"
+    sub "แย" "yae"
+    sub "แร" "rae"
+    sub "แล" "lae"
+    sub "แว" "wae"
+    sub "แศ" "sae"
+    sub "แษ" "sae"
+    sub "แส" "sae"
+    sub "แฬ" "lae"
+    sub "แฮ" "hae"
+    sub "โก" "ko"
+    sub "โกย" "koi"
+    sub "โข" "kho"
+    sub "โขย" "khoi"
+    sub "โฃ" "kho"
+    sub "โฃย" "khoi"
+    sub "โค" "kho"
+    sub "โคย" "khoi"
+    sub "โฅ" "kho"
+    sub "โฅย" "khoi"
+    sub "โฆ" "kho"
+    sub "โฆย" "khoi"
+    sub "โง" "ngo"
+    sub "โงย" "ngoi"
+    sub "โจ" "cho"
+    sub "โจย" "choi"
+    sub "โฉ" "cho"
+    sub "โฉย" "choi"
+    sub "โช" "cho"
+    sub "โชย" "choi"
+    sub "โฌ" "cho"
+    sub "โฌย" "choi"
+    sub "โญ" "yo"
+    sub "โญย" "yoi"
+    sub "โฎ" "do"
+    sub "โฎย" "doi"
+    sub "โฏ" "to"
+    sub "โฏย" "toi"
+    sub "โฐ" "tho"
+    sub "โฐย" "thoi"
+    sub "โฑ" "tho"
+    sub "โฑย" "thoi"
+    sub "โฒ" "tho"
+    sub "โฒย" "thoi"
+    sub "โณ" "no"
+    sub "โณย" "noi"
+    sub "โด" "do"
+    sub "โดย" "doi"
+    sub "โต" "to"
+    sub "โตย" "toi"
+    sub "โถ" "tho"
+    sub "โถย" "thoi"
+    sub "โท" "tho"
+    sub "โทย" "thoi"
+    sub "โธ" "tho"
+    sub "โธย" "thoi"
+    sub "โน" "no"
+    sub "โนย" "noi"
+    sub "โบ" "bo"
+    sub "โบย" "boi"
+    sub "โป" "po"
+    sub "โปย" "poi"
+    sub "โผ" "pho"
+    sub "โผย" "phoi"
+    sub "โฝ" "fo"
+    sub "โฝย" "foi"
+    sub "โพ" "pho"
+    sub "โพย" "phoi"
+    sub "โฟ" "fo"
+    sub "โฟย" "foi"
+    sub "โภ" "pho"
+    sub "โภย" "phoi"
+    sub "โม" "mo"
+    sub "โมย" "moi"
+    sub "โย" "yo"
+    sub "โยย" "yoi"
+    sub "โร" "ro"
+    sub "โรย" "roi"
+    sub "โล" "lo"
+    sub "โลย" "loi"
+    sub "โว" "wo"
+    sub "โวย" "woi"
+    sub "โศ" "so"
+    sub "โศย" "soi"
+    sub "โษ" "so"
+    sub "โษย" "soi"
+    sub "โส" "so"
+    sub "โสย" "soi"
+    sub "โฬ" "lo"
+    sub "โฬย" "loi"
+    sub "โฮ" "ho"
+    sub "โฮย" "hoi"
+    sub "ใก" "kai"
+    sub "ใข" "khai"
+    sub "ใฃ" "khai"
+    sub "ใค" "khai"
+    sub "ใฅ" "khai"
+    sub "ใฆ" "khai"
+    sub "ใง" "ngai"
+    sub "ใจ" "chai"
+    sub "ใฉ" "chai"
+    sub "ใช" "chai"
+    sub "ใฌ" "chai"
+    sub "ใญ" "yai"
+    sub "ใฎ" "dai"
+    sub "ใฏ" "tai"
+    sub "ใฐ" "thai"
+    sub "ใฑ" "thai"
+    sub "ใฒ" "thai"
+    sub "ใณ" "nai"
+    sub "ใด" "dai"
+    sub "ใต" "tai"
+    sub "ใถ" "thai"
+    sub "ใท" "thai"
+    sub "ใธ" "thai"
+    sub "ใน" "nai"
+    sub "ใบ" "bai"
+    sub "ใป" "pai"
+    sub "ใผ" "phai"
+    sub "ใฝ" "fai"
+    sub "ใพ" "phai"
+    sub "ใฟ" "fai"
+    sub "ใภ" "phai"
+    sub "ใม" "mai"
+    sub "ใย" "yai"
+    sub "ใร" "rai"
+    sub "ใล" "lai"
+    sub "ใว" "wai"
+    sub "ใศ" "sai"
+    sub "ใษ" "sai"
+    sub "ใส" "sai"
+    sub "ใฬ" "lai"
+    sub "ใฮ" "hai"
+    sub "ไก" "kai"
+    sub "ไกย" "kai"
+    sub "ไข" "khai"
+    sub "ไขย" "khai"
+    sub "ไฃ" "khai"
+    sub "ไฃย" "khai"
+    sub "ไค" "khai"
+    sub "ไคย" "khai"
+    sub "ไฅ" "khai"
+    sub "ไฅย" "khai"
+    sub "ไฆ" "khai"
+    sub "ไฆย" "khai"
+    sub "ไง" "ngai"
+    sub "ไงย" "ngai"
+    sub "ไจ" "chai"
+    sub "ไจย" "chai"
+    sub "ไฉ" "chai"
+    sub "ไฉย" "chai"
+    sub "ไช" "chai"
+    sub "ไชย" "chai"
+    sub "ไฌ" "chai"
+    sub "ไฌย" "chai"
+    sub "ไญ" "yai"
+    sub "ไญย" "yai"
+    sub "ไฎ" "dai"
+    sub "ไฎย" "dai"
+    sub "ไฏ" "tai"
+    sub "ไฏย" "tai"
+    sub "ไฐ" "thai"
+    sub "ไฐย" "thai"
+    sub "ไฑ" "thai"
+    sub "ไฑย" "thai"
+    sub "ไฒ" "thai"
+    sub "ไฒย" "thai"
+    sub "ไณ" "nai"
+    sub "ไณย" "nai"
+    sub "ได" "dai"
+    sub "ไดย" "dai"
+    sub "ไต" "tai"
+    sub "ไตย" "tai"
+    sub "ไถ" "thai"
+    sub "ไถย" "thai"
+    sub "ไท" "thai"
+    sub "ไทย" "thai"
+    sub "ไธ" "thai"
+    sub "ไธย" "thai"
+    sub "ไน" "nai"
+    sub "ไนย" "nai"
+    sub "ไบ" "bai"
+    sub "ไบย" "bai"
+    sub "ไป" "pai"
+    sub "ไปย" "pai"
+    sub "ไผ" "phai"
+    sub "ไผย" "phai"
+    sub "ไฝ" "fai"
+    sub "ไฝย" "fai"
+    sub "ไพ" "phai"
+    sub "ไพย" "phai"
+    sub "ไฟ" "fai"
+    sub "ไฟย" "fai"
+    sub "ไภ" "phai"
+    sub "ไภย" "phai"
+    sub "ไม" "mai"
+    sub "ไมย" "mai"
+    sub "ไยย" "yai"
+    sub "ไร" "rai"
+    sub "ไรย" "rai"
+    sub "ไล" "lai"
+    sub "ไลย" "lai"
+    sub "ไว" "wai"
+    sub "ไวย" "wai"
+    sub "ไศ" "sai"
+    sub "ไศย" "sai"
+    sub "ไษ" "sai"
+    sub "ไษย" "sai"
+    sub "ไส" "sai"
+    sub "ไสย" "sai"
+    sub "ไฬ" "lai"
+    sub "ไฬย" "lai"
+    sub "ไฮ" "hai"
+    sub "ไฮย" "hai"
+  }
+}
+
+}
diff --git a/maps/alalc-tha-Thai-Latn-2011.isc b/maps/alalc-tha-Thai-Latn-2011.isc
index 1670076..9e04d9e 100644
--- a/maps/alalc-tha-Thai-Latn-2011.isc
+++ b/maps/alalc-tha-Thai-Latn-2011.isc
@@ -36,6 +36,8 @@ tests {
    "\u0e19\u0e04\u0e23" ->  "nkhǭn"
 }
 
+dependency "thai-latn" as thailatn
+
 stage main {
   parallel {
     sub "่" ""
@@ -130,7 +132,175 @@ stage main {
     sub "ทร" "s"
   }
 
-  parallel {
+  use thailatn.leading_vowel_digraphs override {
+      sub "เก" "kē"
+      sub "เข" "khē"
+      sub "เฃ" "khē"
+      sub "เค" "khē"
+      sub "เฅ" "khē"
+      sub "เฆ" "khē"
+      sub "เง" "ngē"
+      sub "เจ" "čhē"
+      sub "เจา" "čhao"
+      sub "เฉ" "chē"
+      sub "เช" "chē"
+      sub "เฌ" "chē"
+      sub "เญ" "yē"
+      sub "เฎ" "dē"
+      sub "เฏ" "tē"
+      sub "เฐ" "thē"
+      sub "เฑ" "thē"
+      sub "เฒ" "thē"
+      sub "เณ" "nē"
+      sub "เด" "dē"
+      sub "เต" "tē"
+      sub "เถ" "thē"
+      sub "เท" "thē"
+      sub "เธ" "thē"
+      sub "เน" "nē"
+      sub "เบ" "bē"
+      sub "เป" "pē"
+      sub "เผ" "phē"
+      sub "เฝ" "fē"
+      sub "เพ" "phē"
+      sub "เฟ" "fē"
+      sub "เภ" "phē"
+      sub "เม" "mē"
+      sub "เย" "yē"
+      sub "เร" "rē"
+      sub "เล" "lē"
+      sub "เว" "wē"
+      sub "เศ" "sē"
+      sub "เษ" "sē"
+      sub "เส" "sē"
+      sub "เฬ" "lē"
+      sub "เฮ" "hē"
+      sub "แก" "kǣ"
+      sub "แข" "khǣ"
+      sub "แฃ" "khǣ"
+      sub "แค" "khǣ"
+      sub "แฅ" "khǣ"
+      sub "แฆ" "khǣ"
+      sub "แง" "ngǣ"
+      sub "แจ" "čhǣ"
+      sub "แฉ" "chǣ"
+      sub "แช" "chǣ"
+      sub "แฌ" "chǣ"
+      sub "แญ" "yǣ"
+      sub "แฎ" "dǣ"
+      sub "แฏ" "tǣ"
+      sub "แฐ" "thǣ"
+      sub "แฑ" "thǣ"
+      sub "แฒ" "thǣ"
+      sub "แณ" "nǣ"
+      sub "แด" "dǣ"
+      sub "แต" "tǣ"
+      sub "แถ" "thǣ"
+      sub "แท" "thǣ"
+      sub "แธ" "thǣ"
+      sub "แน" "nǣ"
+      sub "แบ" "bǣ"
+      sub "แป" "pǣ"
+      sub "แผ" "phǣ"
+      sub "แฝ" "fǣ"
+      sub "แพ" "phǣ"
+      sub "แฟ" "fǣ"
+      sub "แภ" "phǣ"
+      sub "แม" "mǣ"
+      sub "แย" "yǣ"
+      sub "แร" "rǣ"
+      sub "แล" "lǣ"
+      sub "แว" "wǣ"
+      sub "แศ" "sǣ"
+      sub "แษ" "sǣ"
+      sub "แส" "sǣ"
+      sub "แฬ" "lǣ"
+      sub "แฮ" "hǣ"
+      sub "โก" "kō"
+      sub "โกย" "kōi"
+      sub "โข" "khō"
+      sub "โขย" "khōi"
+      sub "โฃ" "khō"
+      sub "โฃย" "khōi"
+      sub "โค" "khō"
+      sub "โคย" "khōi"
+      sub "โฅ" "khō"
+      sub "โฅย" "khōi"
+      sub "โฆ" "khō"
+      sub "โฆย" "khōi"
+      sub "โง" "ngō"
+      sub "โงย" "ngōi"
+      sub "โจ" "čhō"
+      sub "โจย" "čhōi"
+      sub "โฉ" "chō"
+      sub "โฉย" "chōi"
+      sub "โช" "chō"
+      sub "โชย" "chōi"
+      sub "โฌ" "chō"
+      sub "โฌย" "chōi"
+      sub "โญ" "yō"
+      sub "โญย" "yōi"
+      sub "โฎ" "dō"
+      sub "โฎย" "dōi"
+      sub "โฏ" "tō"
+      sub "โฏย" "tōi"
+      sub "โฐ" "thō"
+      sub "โฐย" "thōi"
+      sub "โฑ" "thō"
+      sub "โฑย" "thōi"
+      sub "โฒ" "thō"
+      sub "โฒย" "thōi"
+      sub "โณ" "nō"
+      sub "โณย" "nōi"
+      sub "โด" "dō"
+      sub "โดย" "dōi"
+      sub "โต" "tō"
+      sub "โตย" "tōi"
+      sub "โถ" "thō"
+      sub "โถย" "thōi"
+      sub "โท" "thō"
+      sub "โทย" "thōi"
+      sub "โธ" "thō"
+      sub "โธย" "thōi"
+      sub "โน" "nō"
+      sub "โนย" "nōi"
+      sub "โบ" "bō"
+      sub "โบย" "bōi"
+      sub "โป" "pō"
+      sub "โปย" "pōi"
+      sub "โผ" "phō"
+      sub "โผย" "phōi"
+      sub "โฝ" "fō"
+      sub "โฝย" "fōi"
+      sub "โพ" "phō"
+      sub "โพย" "phōi"
+      sub "โฟ" "fō"
+      sub "โฟย" "fōi"
+      sub "โภ" "phō"
+      sub "โภย" "phōi"
+      sub "โม" "mō"
+      sub "โมย" "mōi"
+      sub "โย" "yō"
+      sub "โยย" "yōi"
+      sub "โร" "rō"
+      sub "โรย" "rōi"
+      sub "โล" "lō"
+      sub "โลย" "lōi"
+      sub "โว" "wō"
+      sub "โวย" "wōi"
+      sub "โศ" "sō"
+      sub "โศย" "sōi"
+      sub "โษ" "sō"
+      sub "โษย" "sōi"
+      sub "โส" "sō"
+      sub "โสย" "sōi"
+      sub "โฬ" "lō"
+      sub "โฬย" "lōi"
+      sub "โฮ" "hō"
+      sub "โฮย" "hōi"
+      sub "ใจ" "čhai"
+      sub "ไจ" "čhai"
+      sub "ไจย" "čhai"
     sub "กะ" "ka"
     sub "ขะ" "kha"
     sub "ฃะ" "kha"
@@ -623,47 +793,6 @@ stage main {
     sub "เษะ" "se"
     sub "เสะ" "se"
     sub "เฮะ" "he"
-    sub "เก" "kē"
-    sub "เข" "khē"
-    sub "เฃ" "khē"
-    sub "เค" "khē"
-    sub "เฅ" "khē"
-    sub "เฆ" "khē"
-    sub "เง" "ngē"
-    sub "เจ" "čhē"
-    sub "เฉ" "chē"
-    sub "เช" "chē"
-    sub "เฌ" "chē"
-    sub "เญ" "yē"
-    sub "เด" "dē"
-    sub "เฎ" "dē"
-    sub "เฑ" "thē"
-    sub "เต" "tē"
-    sub "เฏ" "tē"
-    sub "เถ" "thē"
-    sub "เฐ" "thē"
-    sub "เท" "thē"
-    sub "เธ" "thē"
-    sub "เฒ" "thē"
-    sub "เน" "nē"
-    sub "เณ" "nē"
-    sub "เบ" "bē"
-    sub "เป" "pē"
-    sub "เผ" "phē"
-    sub "เพ" "phē"
-    sub "เภ" "phē"
-    sub "เฝ" "fē"
-    sub "เฟ" "fē"
-    sub "เม" "mē"
-    sub "เย" "yē"
-    sub "เร" "rē"
-    sub "เล" "lē"
-    sub "เฬ" "lē"
-    sub "เว" "wē"
-    sub "เศ" "sē"
-    sub "เษ" "sē"
-    sub "เส" "sē"
-    sub "เฮ" "hē"
     sub "แกะ" "kæ"
     sub "แขะ" "khæ"
     sub "แฃะ" "khæ"
@@ -705,47 +834,6 @@ stage main {
     sub "แษะ" "sæ"
     sub "แสะ" "sæ"
     sub "แฮะ" "hæ"
-    sub "แก" "kǣ"
-    sub "แข" "khǣ"
-    sub "แฃ" "khǣ"
-    sub "แค" "khǣ"
-    sub "แฅ" "khǣ"
-    sub "แฆ" "khǣ"
-    sub "แง" "ngǣ"
-    sub "แจ" "čhǣ"
-    sub "แฉ" "chǣ"
-    sub "แช" "chǣ"
-    sub "แฌ" "chǣ"
-    sub "แญ" "yǣ"
-    sub "แด" "dǣ"
-    sub "แฎ" "dǣ"
-    sub "แฑ" "thǣ"
-    sub "แต" "tǣ"
-    sub "แฏ" "tǣ"
-    sub "แถ" "thǣ"
-    sub "แฐ" "thǣ"
-    sub "แท" "thǣ"
-    sub "แธ" "thǣ"
-    sub "แฒ" "thǣ"
-    sub "แน" "nǣ"
-    sub "แณ" "nǣ"
-    sub "แบ" "bǣ"
-    sub "แป" "pǣ"
-    sub "แผ" "phǣ"
-    sub "แพ" "phǣ"
-    sub "แภ" "phǣ"
-    sub "แฝ" "fǣ"
-    sub "แฟ" "fǣ"
-    sub "แม" "mǣ"
-    sub "แย" "yǣ"
-    sub "แร" "rǣ"
-    sub "แล" "lǣ"
-    sub "แฬ" "lǣ"
-    sub "แว" "wǣ"
-    sub "แศ" "sǣ"
-    sub "แษ" "sǣ"
-    sub "แส" "sǣ"
-    sub "แฮ" "hǣ"
     sub "โกะ" "ko"
     sub "โขะ" "kho"
     sub "โฃะ" "kho"
@@ -787,170 +875,7 @@ stage main {
     sub "โษะ" "so"
     sub "โสะ" "so"
     sub "โฮะ" "ho"
-    sub "โก" "kō"
-    sub "โข" "khō"
-    sub "โฃ" "khō"
-    sub "โค" "khō"
-    sub "โฅ" "khō"
-    sub "โฆ" "khō"
-    sub "โง" "ngō"
-    sub "โจ" "čhō"
-    sub "โฉ" "chō"
-    sub "โช" "chō"
-    sub "โฌ" "chō"
-    sub "โญ" "yō"
-    sub "โด" "dō"
-    sub "โฎ" "dō"
-    sub "โฑ" "thō"
-    sub "โต" "tō"
-    sub "โฏ" "tō"
-    sub "โถ" "thō"
-    sub "โฐ" "thō"
-    sub "โท" "thō"
-    sub "โธ" "thō"
-    sub "โฒ" "thō"
-    sub "โน" "nō"
-    sub "โณ" "nō"
-    sub "โบ" "bō"
-    sub "โป" "pō"
-    sub "โผ" "phō"
-    sub "โพ" "phō"
-    sub "โภ" "phō"
-    sub "โฝ" "fō"
-    sub "โฟ" "fō"
-    sub "โม" "mō"
-    sub "โย" "yō"
-    sub "โร" "rō"
-    sub "โล" "lō"
-    sub "โฬ" "lō"
-    sub "โว" "wō"
-    sub "โศ" "sō"
-    sub "โษ" "sō"
-    sub "โส" "sō"
-    sub "โฮ" "hō"
-    sub "ไก" "kai"
-    sub "ไข" "khai"
-    sub "ไฃ" "khai"
-    sub "ไค" "khai"
-    sub "ไฅ" "khai"
-    sub "ไฆ" "khai"
-    sub "ไง" "ngai"
-    sub "ไจ" "čhai"
-    sub "ไฉ" "chai"
-    sub "ไช" "chai"
-    sub "ไฌ" "chai"
-    sub "ไญ" "yai"
-    sub "ได" "dai"
-    sub "ไฎ" "dai"
-    sub "ไฑ" "thai"
-    sub "ไต" "tai"
-    sub "ไฏ" "tai"
-    sub "ไถ" "thai"
-    sub "ไฐ" "thai"
-    sub "ไท" "thai"
-    sub "ไธ" "thai"
-    sub "ไฒ" "thai"
-    sub "ไน" "nai"
-    sub "ไณ" "nai"
-    sub "ไบ" "bai"
-    sub "ไป" "pai"
-    sub "ไผ" "phai"
-    sub "ไพ" "phai"
-    sub "ไภ" "phai"
-    sub "ไฝ" "fai"
-    sub "ไฟ" "fai"
-    sub "ไม" "mai"
     sub "ไย" "yai"
-    sub "ไร" "rai"
-    sub "ไล" "lai"
-    sub "ไฬ" "lai"
-    sub "ไว" "wai"
-    sub "ไศ" "sai"
-    sub "ไษ" "sai"
-    sub "ไส" "sai"
-    sub "ไฮ" "hai"
-    sub "ใก" "kai"
-    sub "ใข" "khai"
-    sub "ใฃ" "khai"
-    sub "ใค" "khai"
-    sub "ใฅ" "khai"
-    sub "ใฆ" "khai"
-    sub "ใง" "ngai"
-    sub "ใจ" "čhai"
-    sub "ใฉ" "chai"
-    sub "ใช" "chai"
-    sub "ใฌ" "chai"
-    sub "ใญ" "yai"
-    sub "ใด" "dai"
-    sub "ใฎ" "dai"
-    sub "ใฑ" "thai"
-    sub "ใต" "tai"
-    sub "ใฏ" "tai"
-    sub "ใถ" "thai"
-    sub "ใฐ" "thai"
-    sub "ใท" "thai"
-    sub "ใธ" "thai"
-    sub "ใฒ" "thai"
-    sub "ใน" "nai"
-    sub "ใณ" "nai"
-    sub "ใบ" "bai"
-    sub "ใป" "pai"
-    sub "ใผ" "phai"
-    sub "ใพ" "phai"
-    sub "ใภ" "phai"
-    sub "ใฝ" "fai"
-    sub "ใฟ" "fai"
-    sub "ใม" "mai"
-    sub "ใย" "yai"
-    sub "ใร" "rai"
-    sub "ใล" "lai"
-    sub "ใฬ" "lai"
-    sub "ใว" "wai"
-    sub "ใศ" "sai"
-    sub "ใษ" "sai"
-    sub "ใส" "sai"
-    sub "ใฮ" "hai"
-    sub "ไกย" "kai"
-    sub "ไขย" "khai"
-    sub "ไฃย" "khai"
-    sub "ไคย" "khai"
-    sub "ไฅย" "khai"
-    sub "ไฆย" "khai"
-    sub "ไงย" "ngai"
-    sub "ไจย" "čhai"
-    sub "ไฉย" "chai"
-    sub "ไชย" "chai"
-    sub "ไฌย" "chai"
-    sub "ไญย" "yai"
-    sub "ไดย" "dai"
-    sub "ไฎย" "dai"
-    sub "ไฑย" "thai"
-    sub "ไตย" "tai"
-    sub "ไฏย" "tai"
-    sub "ไถย" "thai"
-    sub "ไฐย" "thai"
-    sub "ไทย" "thai"
-    sub "ไธย" "thai"
-    sub "ไฒย" "thai"
-    sub "ไนย" "nai"
-    sub "ไณย" "nai"
-    sub "ไบย" "bai"
-    sub "ไปย" "pai"
-    sub "ไผย" "phai"
-    sub "ไพย" "phai"
-    sub "ไภย" "phai"
-    sub "ไฝย" "fai"
-    sub "ไฟย" "fai"
-    sub "ไมย" "mai"
-    sub "ไยย" "yai"
-    sub "ไรย" "rai"
-    sub "ไลย" "lai"
-    sub "ไฬย" "lai"
-    sub "ไวย" "wai"
-    sub "ไศย" "sai"
-    sub "ไษย" "sai"
-    sub "ไสย" "sai"
-    sub "ไฮย" "hai"
     sub "ใกย" "kai"
     sub "ใขย" "khai"
     sub "ใฃย" "khai"
@@ -1074,47 +999,6 @@ stage main {
     sub "ษาย" "sāi"
     sub "สาย" "sāi"
     sub "ฮาย" "hāi"
-    sub "เกา" "kao"
-    sub "เขา" "khao"
-    sub "เฃา" "khao"
-    sub "เคา" "khao"
-    sub "เฅา" "khao"
-    sub "เฆา" "khao"
-    sub "เงา" "ngao"
-    sub "เจา" "čhao"
-    sub "เฉา" "chao"
-    sub "เชา" "chao"
-    sub "เฌา" "chao"
-    sub "เญา" "yao"
-    sub "เดา" "dao"
-    sub "เฎา" "dao"
-    sub "เฑา" "thao"
-    sub "เตา" "tao"
-    sub "เฏา" "tao"
-    sub "เถา" "thao"
-    sub "เฐา" "thao"
-    sub "เทา" "thao"
-    sub "เธา" "thao"
-    sub "เฒา" "thao"
-    sub "เนา" "nao"
-    sub "เณา" "nao"
-    sub "เบา" "bao"
-    sub "เปา" "pao"
-    sub "เผา" "phao"
-    sub "เพา" "phao"
-    sub "เภา" "phao"
-    sub "เฝา" "fao"
-    sub "เฟา" "fao"
-    sub "เมา" "mao"
-    sub "เยา" "yao"
-    sub "เรา" "rao"
-    sub "เลา" "lao"
-    sub "เฬา" "lao"
-    sub "เวา" "wao"
-    sub "เศา" "sao"
-    sub "เษา" "sao"
-    sub "เสา" "sao"
-    sub "เฮา" "hao"
     sub "กาว" "kāo"
     sub "ขาว" "khāo"
     sub "ฃาว" "khāo"
@@ -1197,47 +1081,6 @@ stage main {
     sub "ษุย" "sui"
     sub "สุย" "sui"
     sub "ฮุย" "hui"
-    sub "โกย" "kōi"
-    sub "โขย" "khōi"
-    sub "โฃย" "khōi"
-    sub "โคย" "khōi"
-    sub "โฅย" "khōi"
-    sub "โฆย" "khōi"
-    sub "โงย" "ngōi"
-    sub "โจย" "čhōi"
-    sub "โฉย" "chōi"
-    sub "โชย" "chōi"
-    sub "โฌย" "chōi"
-    sub "โญย" "yōi"
-    sub "โดย" "dōi"
-    sub "โฎย" "dōi"
-    sub "โฑย" "thōi"
-    sub "โตย" "tōi"
-    sub "โฏย" "tōi"
-    sub "โถย" "thōi"
-    sub "โฐย" "thōi"
-    sub "โทย" "thōi"
-    sub "โธย" "thōi"
-    sub "โฒย" "thōi"
-    sub "โนย" "nōi"
-    sub "โณย" "nōi"
-    sub "โบย" "bōi"
-    sub "โปย" "pōi"
-    sub "โผย" "phōi"
-    sub "โพย" "phōi"
-    sub "โภย" "phōi"
-    sub "โฝย" "fōi"
-    sub "โฟย" "fōi"
-    sub "โมย" "mōi"
-    sub "โยย" "yōi"
-    sub "โรย" "rōi"
-    sub "โลย" "lōi"
-    sub "โฬย" "lōi"
-    sub "โวย" "wōi"
-    sub "โศย" "sōi"
-    sub "โษย" "sōi"
-    sub "โสย" "sōi"
-    sub "โฮย" "hōi"
     sub "กอย" "kǭi"
     sub "ขอย" "khǭi"
     sub "ฃอย" "khǭi"
diff --git a/maps/bgnpcgn-tha-Thai-Latn-2002.isc b/maps/bgnpcgn-tha-Thai-Latn-2002.isc
index 525604e..88a3b7a 100644
--- a/maps/bgnpcgn-tha-Thai-Latn-2002.isc
+++ b/maps/bgnpcgn-tha-Thai-Latn-2002.isc
@@ -43,6 +43,8 @@ tests {
 }
 
 
+dependency "thai-latn" as thailatn
+
 stage main {
 
   # MARKS (tone marks are not romanized; the vowel shortening mark ็
@@ -112,351 +114,24 @@ stage main {
   # pronounced" (แขนง → khanaeng, เขื่อยา → khayao). One enumerated
   # digraph row per consonant, as in the corpus's ALA-LC Thai 2011
   # encoding; rows sit before the consonant and vowel passes.
-  parallel {
-    sub "ไกย" "kai"
-    sub "ไขย" "khai"
-    sub "ไฆย" "khai"
-    sub "ไคย" "khai"
-    sub "ไฅย" "khai"
-    sub "ไฃย" "khai"
-    sub "ไงย" "ngai"
-    sub "ไจย" "chai"
-    sub "ไฉย" "chai"
-    sub "ไชย" "chai"
-    sub "ไฌย" "chai"
-    sub "ไญย" "yai"
-    sub "ไฎย" "dai"
-    sub "ไฏย" "tai"
-    sub "ไฑย" "thai"
-    sub "ไฒย" "thai"
-    sub "ไดย" "dai"
-    sub "ไตย" "tai"
-    sub "ไฐย" "thai"
-    sub "ไถย" "thai"
-    sub "ไทย" "thai"
-    sub "ไธย" "thai"
-    sub "ไณย" "nai"
-    sub "ไนย" "nai"
-    sub "ไบย" "bai"
-    sub "ไปย" "pai"
-    sub "ไผย" "phai"
-    sub "ไพย" "phai"
-    sub "ไภย" "phai"
-    sub "ไฝย" "fai"
-    sub "ไฟย" "fai"
-    sub "ไมย" "mai"
-    sub "ไยย" "yai"
-    sub "ไรย" "rai"
-    sub "ไลย" "lai"
-    sub "ไฬย" "lai"
-    sub "ไวย" "wai"
+  use thailatn.leading_vowel_digraphs override {
     sub "ไซย" "sai"
-    sub "ไศย" "sai"
-    sub "ไษย" "sai"
-    sub "ไสย" "sai"
     sub "ไหย" "hai"
-    sub "ไฮย" "hai"
-    sub "โกย" "koi"
-    sub "โขย" "khoi"
-    sub "โฆย" "khoi"
-    sub "โคย" "khoi"
-    sub "โฅย" "khoi"
-    sub "โฃย" "khoi"
-    sub "โงย" "ngoi"
-    sub "โจย" "choi"
-    sub "โฉย" "choi"
-    sub "โชย" "choi"
-    sub "โฌย" "choi"
-    sub "โญย" "yoi"
-    sub "โฎย" "doi"
-    sub "โฏย" "toi"
-    sub "โฑย" "thoi"
-    sub "โฒย" "thoi"
-    sub "โดย" "doi"
-    sub "โตย" "toi"
-    sub "โฐย" "thoi"
-    sub "โถย" "thoi"
-    sub "โทย" "thoi"
-    sub "โธย" "thoi"
-    sub "โณย" "noi"
-    sub "โนย" "noi"
-    sub "โบย" "boi"
-    sub "โปย" "poi"
-    sub "โผย" "phoi"
-    sub "โพย" "phoi"
-    sub "โภย" "phoi"
-    sub "โฝย" "foi"
-    sub "โฟย" "foi"
-    sub "โมย" "moi"
-    sub "โยย" "yoi"
-    sub "โรย" "roi"
-    sub "โลย" "loi"
-    sub "โฬย" "loi"
-    sub "โวย" "woi"
     sub "โซย" "soi"
-    sub "โศย" "soi"
-    sub "โษย" "soi"
-    sub "โสย" "soi"
     sub "โหย" "hoi"
-    sub "โฮย" "hoi"
-    sub "เกา" "kao"
-    sub "เขา" "khao"
-    sub "เฆา" "khao"
-    sub "เคา" "khao"
-    sub "เฅา" "khao"
-    sub "เฃา" "khao"
-    sub "เงา" "ngao"
-    sub "เจา" "chao"
-    sub "เฉา" "chao"
-    sub "เชา" "chao"
-    sub "เฌา" "chao"
-    sub "เญา" "yao"
-    sub "เฎา" "dao"
-    sub "เฏา" "tao"
-    sub "เฑา" "thao"
-    sub "เฒา" "thao"
-    sub "เดา" "dao"
-    sub "เตา" "tao"
-    sub "เฐา" "thao"
-    sub "เถา" "thao"
-    sub "เทา" "thao"
-    sub "เธา" "thao"
-    sub "เณา" "nao"
-    sub "เนา" "nao"
-    sub "เบา" "bao"
-    sub "เปา" "pao"
-    sub "เผา" "phao"
-    sub "เพา" "phao"
-    sub "เภา" "phao"
-    sub "เฝา" "fao"
-    sub "เฟา" "fao"
-    sub "เมา" "mao"
-    sub "เยา" "yao"
-    sub "เรา" "rao"
-    sub "เลา" "lao"
-    sub "เฬา" "lao"
-    sub "เวา" "wao"
     sub "เซา" "sao"
-    sub "เศา" "sao"
-    sub "เษา" "sao"
-    sub "เสา" "sao"
     sub "เหา" "hao"
-    sub "เฮา" "hao"
-    sub "ไก" "kai"
-    sub "ไข" "khai"
-    sub "ไฆ" "khai"
-    sub "ไค" "khai"
-    sub "ไฅ" "khai"
-    sub "ไฃ" "khai"
-    sub "ไง" "ngai"
-    sub "ไจ" "chai"
-    sub "ไฉ" "chai"
-    sub "ไช" "chai"
-    sub "ไฌ" "chai"
-    sub "ไญ" "yai"
-    sub "ไฎ" "dai"
-    sub "ไฏ" "tai"
-    sub "ไฑ" "thai"
-    sub "ไฒ" "thai"
-    sub "ได" "dai"
-    sub "ไต" "tai"
-    sub "ไฐ" "thai"
-    sub "ไถ" "thai"
-    sub "ไท" "thai"
-    sub "ไธ" "thai"
-    sub "ไณ" "nai"
-    sub "ไน" "nai"
-    sub "ไบ" "bai"
-    sub "ไป" "pai"
-    sub "ไผ" "phai"
-    sub "ไพ" "phai"
-    sub "ไภ" "phai"
-    sub "ไฝ" "fai"
-    sub "ไฟ" "fai"
-    sub "ไม" "mai"
     sub "ไย" "yai"
-    sub "ไร" "rai"
-    sub "ไล" "lai"
-    sub "ไฬ" "lai"
-    sub "ไว" "wai"
     sub "ไซ" "sai"
-    sub "ไศ" "sai"
-    sub "ไษ" "sai"
-    sub "ไส" "sai"
     sub "ไห" "hai"
-    sub "ไฮ" "hai"
-    sub "ใก" "kai"
-    sub "ใข" "khai"
-    sub "ใฆ" "khai"
-    sub "ใค" "khai"
-    sub "ใฅ" "khai"
-    sub "ใฃ" "khai"
-    sub "ใง" "ngai"
-    sub "ใจ" "chai"
-    sub "ใฉ" "chai"
-    sub "ใช" "chai"
-    sub "ใฌ" "chai"
-    sub "ใญ" "yai"
-    sub "ใฎ" "dai"
-    sub "ใฏ" "tai"
-    sub "ใฑ" "thai"
-    sub "ใฒ" "thai"
-    sub "ใด" "dai"
-    sub "ใต" "tai"
-    sub "ใฐ" "thai"
-    sub "ใถ" "thai"
-    sub "ใท" "thai"
-    sub "ใธ" "thai"
-    sub "ใณ" "nai"
-    sub "ใน" "nai"
-    sub "ใบ" "bai"
-    sub "ใป" "pai"
-    sub "ใผ" "phai"
-    sub "ใพ" "phai"
-    sub "ใภ" "phai"
-    sub "ใฝ" "fai"
-    sub "ใฟ" "fai"
-    sub "ใม" "mai"
-    sub "ใย" "yai"
-    sub "ใร" "rai"
-    sub "ใล" "lai"
-    sub "ใฬ" "lai"
-    sub "ใว" "wai"
     sub "ใซ" "sai"
-    sub "ใศ" "sai"
-    sub "ใษ" "sai"
-    sub "ใส" "sai"
     sub "ให" "hai"
-    sub "ใฮ" "hai"
-    sub "โก" "ko"
-    sub "โข" "kho"
-    sub "โฆ" "kho"
-    sub "โค" "kho"
-    sub "โฅ" "kho"
-    sub "โฃ" "kho"
-    sub "โง" "ngo"
-    sub "โจ" "cho"
-    sub "โฉ" "cho"
-    sub "โช" "cho"
-    sub "โฌ" "cho"
-    sub "โญ" "yo"
-    sub "โฎ" "do"
-    sub "โฏ" "to"
-    sub "โฑ" "tho"
-    sub "โฒ" "tho"
-    sub "โด" "do"
-    sub "โต" "to"
-    sub "โฐ" "tho"
-    sub "โถ" "tho"
-    sub "โท" "tho"
-    sub "โธ" "tho"
-    sub "โณ" "no"
-    sub "โน" "no"
-    sub "โบ" "bo"
-    sub "โป" "po"
-    sub "โผ" "pho"
-    sub "โพ" "pho"
-    sub "โภ" "pho"
-    sub "โฝ" "fo"
-    sub "โฟ" "fo"
-    sub "โม" "mo"
-    sub "โย" "yo"
-    sub "โร" "ro"
-    sub "โล" "lo"
-    sub "โฬ" "lo"
-    sub "โว" "wo"
     sub "โซ" "so"
-    sub "โศ" "so"
-    sub "โษ" "so"
-    sub "โส" "so"
     sub "โห" "ho"
-    sub "โฮ" "ho"
-    sub "เก" "ke"
-    sub "เข" "khe"
-    sub "เฆ" "khe"
-    sub "เค" "khe"
-    sub "เฅ" "khe"
-    sub "เฃ" "khe"
-    sub "เง" "nge"
-    sub "เจ" "che"
-    sub "เฉ" "che"
-    sub "เช" "che"
-    sub "เฌ" "che"
-    sub "เญ" "ye"
-    sub "เฎ" "de"
-    sub "เฏ" "te"
-    sub "เฑ" "the"
-    sub "เฒ" "the"
-    sub "เด" "de"
-    sub "เต" "te"
-    sub "เฐ" "the"
-    sub "เถ" "the"
-    sub "เท" "the"
-    sub "เธ" "the"
-    sub "เณ" "ne"
-    sub "เน" "ne"
-    sub "เบ" "be"
-    sub "เป" "pe"
-    sub "เผ" "phe"
-    sub "เพ" "phe"
-    sub "เภ" "phe"
-    sub "เฝ" "fe"
-    sub "เฟ" "fe"
-    sub "เม" "me"
-    sub "เย" "ye"
-    sub "เร" "re"
-    sub "เล" "le"
-    sub "เฬ" "le"
-    sub "เว" "we"
     sub "เซ" "se"
-    sub "เศ" "se"
-    sub "เษ" "se"
-    sub "เส" "se"
     sub "เห" "he"
-    sub "เฮ" "he"
-    sub "แก" "kae"
-    sub "แข" "khae"
-    sub "แฆ" "khae"
-    sub "แค" "khae"
-    sub "แฅ" "khae"
-    sub "แฃ" "khae"
-    sub "แง" "ngae"
-    sub "แจ" "chae"
-    sub "แฉ" "chae"
-    sub "แช" "chae"
-    sub "แฌ" "chae"
-    sub "แญ" "yae"
-    sub "แฎ" "dae"
-    sub "แฏ" "tae"
-    sub "แฑ" "thae"
-    sub "แฒ" "thae"
-    sub "แด" "dae"
-    sub "แต" "tae"
-    sub "แฐ" "thae"
-    sub "แถ" "thae"
-    sub "แท" "thae"
-    sub "แธ" "thae"
-    sub "แณ" "nae"
-    sub "แน" "nae"
-    sub "แบ" "bae"
-    sub "แป" "pae"
-    sub "แผ" "phae"
-    sub "แพ" "phae"
-    sub "แภ" "phae"
-    sub "แฝ" "fae"
-    sub "แฟ" "fae"
-    sub "แม" "mae"
-    sub "แย" "yae"
-    sub "แร" "rae"
-    sub "แล" "lae"
-    sub "แฬ" "lae"
-    sub "แว" "wae"
     sub "แซ" "sae"
-    sub "แศ" "sae"
-    sub "แษ" "sae"
-    sub "แส" "sae"
     sub "แห" "hae"
-    sub "แฮ" "hae"
   }
 
   # COMPOUND VOWEL SIGNS (adjacent-sign forms; source rows 10-19)