This International Standard establishes a system for the transliteration¹⁾ of Thai characters into Roman characters. One set of rules is provided for a completely reversible stringent conversion where principles of transliteration are applied without exception.

This Romanized transliteration system is a means of converting the Thai writing system into a Roman alphabet writing system. Since there are fewer Roman characters than Thai characters, diacritical marks, punctuation marks, and a combination of two Roman characters, or a digraph, are needed to represent one Thai character. The aim of this system is to provide a means of international communication of written messages in a form which permits the automatic transmission or reconstitution of these by men or machines. This system of conversion is intended to provide complete and unambiguous reversibility. It is possible that the results obtained from this system will not provide for correct pronunciation of the original Thai text. However, they will serve as a means of finding the Thai graphisms automatically and thus to allow anyone with a knowledge of Thai to pronounce the Thai text correctly. An attempt to transpose a preposed vowel after an initial consonant may comfort those who are used to the Roman writing system where a vowel always follows a consonant to form a syllable, unless it is a syllable without an initial. It is best to leave the preposed vowel in the Thai transliteration system where it is, because a transliteration system is not a transcription system.

Capital letters are reserved for writing the initial in proper nouns. It is unwise to make use of capital letters in the transliteration system for certain characters, otherwise common nouns and proper nouns cannot be distinguished from one another.

This system is based on phonetic logic in the selection of transliterated representations, as much as possible, in order to lessen the burden on those who wish to learn the system.

1) Definitions, explanations for terms used (transliteration, transcription, etc.) appear in annex A.