The Royal Thai General System of Transcription (RTGS; ) is the official system for rendering Thai words in the Latin script. It was published by the Royal Institute of Thailand in early 1917, when Thailand was called Siam.

It is used in road signs and government publications and is the closest method to a standard of transcription for Thai, but its use, even by the government, is inconsistent. The system is almost identical to the one that is defined by ISO 11940-2.

Features

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: , , , , .
  • Single letters , , , , are monophthongs (simple vowels), with the same value as in the International Phonetic Alphabet (IPA).
  • Digraphs with trailing are monophthongs; , , sound like respectively.
  • Digraphs and trigraphs with trailing , , are diphthongs and indicate IPA respectively.
  • It uses consonants as in IPA except as follows:
  • Digraphs with (, , ) are aspirated consonants to distinguish them from unaspirated , , .
  • It uses for , as in English.
  • It uses for and , somewhat like English.
  • It uses for , 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 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, Institute of Thai Studies is transcribed as . However, compounds and names of persons are written without spaces between words. For example, (from + , 'scout') is transcribed as , not , and , the first and last names of a person, is transcribed as , not .

  1. The general system should be expandable to the precise system.
  2. The general system should be based on pronunciation, and one sound should be represented by one symbol or letter.
  3. The general system should be in consonance with the principles of Thai grammar, orthography, and pronunciation.
  4. In selecting symbols or letters, account should be taken of existing types for printing and typewriting and of existing systems of transcription.

The committee considered that for the general system, tone and quantity marks were unneeded. They would be provided for the precise system. and IPA notation (æ, ǫ).|| oe with the other stops and is used as such in ISO 11940-2.

  • The notation does not differentiate between IPA and IPA (see table below).

{| class="wikitable"

! 

! colspan="4" |Phoneme 1 !! colspan="4" |Phoneme 2

|-

! RTGS

! Thai!!IPA!!Description!!English

! Thai!!IPA!!Description!!English

|-

| ch

|

|

| alveo-palatal<br />affricate

| roughly like in "let you"<br />

| , ,

|

| aspirated alveo-<br />palatal affricate

| roughly like in "check"

|-

| rowspan="2" |o

| ,

|

| close-mid back<br />short rounded

| like the vowel in "note" <br />(American pronunciation)

|

|

| open-mid back<br />short rounded

| like in "boy"

|-

|

|

| close-mid back<br />long rounded

| like in "go" (Scottish English)

|

|

| open-mid back<br />long rounded

| like in "raw"

|}

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.