RTGS and the ThaiVisa Modification

[Richard W]

When the Thai language forum was new, back in 2004, we devised a method of transcribing Thai that is at least as accurate as Thai orthography. We took the Royal Thai General System (the dominant system on road signs in Thailand) and fixed its faults while still just using case-insensitive ASCII characters. The form as finally practised differs from the RTGS as follows:

• It shows tone (by letter M, L, F, H, R in square brackets before the syllable)
• It shows length (by L or S in those square brackets, or doubling the letter in a one-letter vowel symbol to specify the long vowel).
  • i and o after a different vowel do not count as part of the vowel symbol
  • 1-letter vowel symbols are short by default
  • 2-letter (or longer) vowel symbols are long by default - works well for 'ia', 'uea', 'ua', 'ae', 'oe' and 'aw'/'or' and fairly well for 'ue'
• It distinguishes vowel sound represented, when long, by the letter อ as 'aw'
• It distinguish consonant sound of จ cho chan as 'j'
• It allows both 'k' and 'g' for the sound of ก ko kai.

Thus we transcribe เห็ด 'mushroom' and เหตุ 'reason', which the RTGS transcribes as het, as [L]het and [L]heet. Note that if there is no other tone indicator in the square brackets, an 'L' must be a tone indicator, not a length mark. Indeed, the only good reason for using 'L' as a length marker is to preserve the simple writing, e.g. when transcribing แม่สาย 'Mae Sai' as [F]Mae [RL]Sai rather than [F]Mae [R]Saai. On the other hand, 'S' is needed for words like เงิน [MS]ngoen 'money' and แข็ง [RS]khaeng 'hard'.

The letters for the tones relate to the standard Thai tones as follows:
กา=[M]kaa ก่า=[L]kaa ก้า=[F]kaa ก๊า=[H]kaa ก๋า=[R]kaa
Note that the correspondence is by sound, not by mark; ม้า=[H]maa.

While the above is a complete description of the system for those who are familiar with the RTGS, for completeness I will now provide tables relating the RTGS and the ThaiVisa modification back to Thai spelling. Note, however, that both systems represent the sound of words; the tables do not cover quirky spellings. For that reason, no entries are made for ฤ or ฤๅ.

The symbols for long vowels relate as follows:


The symbols for short vowels in 'open' syllables relate as follows:

Note that the glottal stops (denoted by 'ʔ' in IPA) are normally omitted in unstressed syllables.

The symbols for short vowels in closed syllables relate as follows:


Some vowel symbols also incorporate the final consonant. These and related and special sequences relate as follow:


The initial consonants relate as follows:

The letter ฑ tho montho appears twice, for there is a small group of words in which it pronounced like ด, such as บัณฑิต [M]ban[L]dit 'graduate, bachelor, pandit'. I have not included ห nam, อ nam or clusters with silent ร. Arguably ห nam and อ nam are represented in the transcription by their effect on the tone.

For completeness, I include the list of final consonants, ignoring random non-occurrences:


Finally, for the convenience of anyone wishing to quote sections of these tables, I include the LibreOffice file in which I composed the tables. I am attaching it as a Word document. If Word can't open it directly, save the file to disk and rename with extension '.odt'. The attachment is RTGS_TV_ext.doc.