Royal Thai General System of Transcription

Prominent features of the system are:

• It uses only unmodified letters from the Latin alphabet without diacritics.
• It spells all vowels and diphthongs with vowel letters: ⟨a⟩, ⟨e⟩, ⟨i⟩, ⟨o⟩, ⟨u⟩.
  • Single letters ⟨a⟩, ⟨e⟩, ⟨i⟩, ⟨o⟩, ⟨u⟩ are monophthongs (simple vowels), with the same value as in the International Phonetic Alphabet (IPA).
  • Digraphs with trailing ⟨e⟩ are monophthongs; ⟨ae⟩, ⟨oe⟩, ⟨ue⟩ sound like /ɛ, ɤ, ɯ/ respectively.
  • Digraphs and trigraphs with trailing ⟨a⟩, ⟨i⟩, ⟨o⟩ are diphthongs and indicate IPA /a, j, w/ respectively.
• It uses consonants as in IPA except as follows:
  • Digraphs with ⟨h⟩ (⟨ph⟩, ⟨th⟩, ⟨kh⟩) are aspirated /pʰ, tʰ, kʰ/ consonants to distinguish them from unaspirated ⟨p⟩, ⟨t⟩, ⟨k⟩.
  • It uses ⟨ng⟩ for /ŋ/, as in English.
  • It uses ⟨ch⟩ for /t͡ɕʰ/ and /t͡ɕ/, somewhat like English.
  • It uses ⟨y⟩ for /j/, as in English.

Final consonants are transcribed according to pronunciation, not Thai orthography.

Vowels are transcribed in the position in the word where they are pronounced, not as in Thai orthography. Implied vowels, which are not written in Thai orthography, are transcribed as pronounced.

A hyphen is used to avoid ambiguity in syllable separation before a succeeding syllable that starts with a vowel and before ⟨ng⟩ if the preceding syllable ends with a vowel.

Transcribed words are written with spaces between them although there are no spaces in Thai. For example, "สถาบันไทยคดีศึกษา" Institute of Thai Studies is transcribed as "Sathaban Thai Khadi Sueksa". However, compounds and names of persons are written without spaces between words. For example, "ลูกเสือ" (from "ลูก" + "เสือ", scout) is transcribed as "luksuea", not "luk suea", and "โชคชัย จิตงาม", the first and last names of a person, is transcribed as "Chokchai Chitngam", not "Chok Chai Chit Ngam".[1]

For consonants, the transcriptions are given for both initial and final position in the syllable. For vowels, a dash ("–") indicates the relative position of the vowel's initial consonant.

There have been four versions of the RTGS, those promulgated in 1932, 1939, 1968 and 1999. The general system was issued by the Ministry of Public Instruction in 1932, and subsequent issues have been issued by the Royal Institute of Thailand.

The system does not transcribe all features of Thai phonology. Particularly it has the following shortcomings:

• It does not record tones.
• It does not differentiate between short and long vowels.
• The notation ⟨ch⟩ does not differentiate between IPA /t͡ɕ/ and IPA /t͡ɕʰ/ (see table below). Using ⟨c⟩ for /t͡ɕ/ would have been more consistent[10] with the other stops and is used as such in ISO 11940-2.
• The notation ⟨o⟩ does not differentiate between IPA /ɔ/ and IPA /o/ (see table below).

The original design envisioned the general system to give broad details of pronunciation, and the precise system to supplement that with vowel lengths, tones, and specific Thai characters used.[7] The ambiguity of ⟨ch⟩ and ⟨o⟩ was introduced in the 1968 version.

• ISO 11940
• ISO 11940-2
• Thai transliteration

• Discussion of romanisation (Microsoft Word document)
• Downloadable Windows-based transcription tool
• ALA-LC: PDF guide to romanization of Thai (U.S. library of Congress)