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.
Table of changes 1932 version The general system was set up by a committee of the
Ministry of Public Instruction on the following principles: • The general system should be expandable to the precise system. • The general system should be based on pronunciation, and one sound should be represented by one symbol or letter. • The general system should be in consonance with the principles of Thai grammar, orthography, and pronunciation. • 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).
Relationship to precise system The precise system was issued along with the general system in 1939. A transliteration in the precise system could be converted to the general system by doing the following: • Removing parenthesised character • Replacing
ʽ and
hʽ by
h • Removing length and tone markings • Removing
ḥ, which corresponds to , which may be viewed as a length mark • Removing the character distinguishing dots below and primes • Changing
ay and
aiy to
ai except before vowels • Changing
č to
čh • Changing
ie to
ia,
uo to
ua and
ưœ to
ưa The last set of changes removes a graphic distinction between vowels in closed syllables and vowels in open syllables. The
h is added to
č in the general system to make it easier to read. When the diacritic was subsequently removed, the
h was justified as avoiding the misreading of the transliteration as or rather than the correct .
1968 version The 1968 version removed diacritics, including the horn of
ư and replaced the ligatures
æ and
œ by
ae and
oe. While that is more suitable as the standard transliteration for maps, it removed the contrast between the transcriptions of and , and , and , and and .
1999 version The 1999 version restored the distinction between the transcriptions of the pairs and and and . It also simplified the transliteration of final , which now is always transcribed .
Allowed variants The following variants have been allowed: ==Criticism==