There are many systems for the romanization of the Thai language, i.e. representing the language in Latin script. These include systems of transliteration, and transcription. The most seen system in public space is Royal Thai General System of Transcription (RTGS)—the official scheme promulgated by the Royal Thai Institute. It is based on spoken Thai, but disregards tone, vowel length and a few minor sound distinctions.
The international standard ISO 11940 is a transliteration system, preserving all aspects of written Thai adding diacritics to the Roman letters. Its extension ISO 11940-2 defines a simplified transcription reflecting the spoken language. It is almost identical to RTGS. Libraries in English-speaking countries use the ALA-LC Romanization.
In practice, often non-standard and inconsistent romanizations are used, especially for proper nouns and personal names. This is reflected, for example, in the name Suvarnabhumi Airport, which is spelled based on direct transliteration of the name's Sanskrit root. Language learning books often use their own proprietary systems, none of which are used in Thai public space.