Prominent features of the system are: Final consonants are transcribed according to pronunciation, not Thai orthography.
Implied vowels, which are not written in Thai orthography, are transcribed as pronounced.
When the diacritic was subsequently removed, the h was justified as avoiding the misreading of the transliteration as /k/ or /s/ rather than the correct /tɕ/.
[3] 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 จ /tɕ/ and ช /tɕʰ/, อึ /ɯ/ and อุ /u/, เอือ /ɯa/ and อัว /ua/, and โอ /oː/ and ออ /ɔː/.
Particularly it has the following shortcomings: 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.