Thai can be a daunting language to learn so here are some Thai Language Facts:

Area Dialects

Standard or Central Thai, spoken by about 25 million (1990), is the official dialect of Thailand.

Bangkok Thai can be included in Standard Thai or considered as a separate dialect.

Khorat. Spoken by about 400,000 (1984) in Nakhon Ratchasima.

Isan (north-eastern). The dialect of the Isan region of Thailand is sometimes considered a dialect of the Laotian language, which it closely resembles. Spoken by about 15 million (1983).

Thai Yuan or Lanna (northern), spoken by about 6 million (1983).
Southern, Pak Thai, or Dambro: spoken about 5 million (1990).

Malay or Pattani. Spoken by 3 million (1998) in southern Thailand.

Tai Dam. Spoken by about 500,000 (1990) in Vietnam.

Tai Daeng. Spoken by about 125,000 (1990) in Vietnam and elsewhere.

Phuan or Phu Thai. Spoken by about 400,000 (1993), mostly outside Thailand.

Lue(Dai). Spoken by about 78,000 (1993) in Thailand, and 250,000 to 1 million in China.

Song. Spoken by about 20,000 to 30,000 (1982).

Shan. Spoken by about 3 million (1993) in Myanmar.

Statistics from Ethnologue 2003-10-4. Most speakers of dialects and minority languages speak Central Thai in addition. Central Thai is the dielect taught in schools and the local dielect would be spoken at home.

Thai alphabet
The Thai alphabet (q.v. for full details) is probably derived from the Old Khmer (??????????) script, which is a southern Brahmic script of the Indic family, and is quite complex from the perspective of Unicode and computer text rendering, because: It is an abugida script, in which the default vowel is a long O. Vowels associated with consonants are nonsequential: they can precede, follow, or surround their associated consonant(s). Tone markers can occur at several places relative to the vowel grapheme.