text: The Royal Thai General System of Transcription (RTGS) is the official system for rendering Thai words in the Latin alphabet. 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 , , .