Thai (ภาษาไทย phaasǎa Thai) is the official language of Thailand and the native language of the Thai people around the world.
Thai is member of the Tai-Kadai language family, just like Lao, with which the language is closely related. There are several different dialects are spoken in the distinct regions of the country, namely the central, northern and southern dialects. The northeast speaks a different language, the Isaan language, which is, with minor differences in vocabulary aside, virtually identical to Lao.
Thai is a tonal language with five tones: Mid, Low, Falling, High, and Rising. Meanings can change critically based on the tone, but Thais are fairly used to hearing foreigners mangle their language and can often work out the correct tone based on context. Try not to inflect your sentences; in particular, any questions should be pronounced as flat statements, without the rising intonation ("...yes?") typical to English questions.
The Thai written language is essentially alphabetic, but notoriously difficult to read due to a profusion of 44 consonants (many redundant), complicated tone and vowel signage around consonants and a complete lack of spaces between words.
Thai has a complicated set of vowels and diphthongs that distinguishes between vowel length (short and long) and vowel position (front and back). In Thai script, vowel signs are always written around consonants and the letter ก (k) is used here to demonstrate. This list follows the Royal Thai General System of Transcription (except that some long vowels are doubled).
like 'a' in "car" (short vowel)
like 'a' in "father" (longer than "a")
like 'a' in "man" (short vowel: "แกะ")
like 'e' in "bed" (short vowel: "เกะ")
like 'y' in "greedy"
like 'ee' in "see" (longer than "i")
like 'o' in "torn" (short vowel: "เกาะ")
like 'oa' in "moan" (short vowel: "โกะ")
like 'i' in "sir" (short vowel: "เกอะ")
like 'oo' in "hoop"
like 'ue' in "blue" (longer than "u")
frontal version of "u" (akin to German "ü", French "du", not found in English) (short vowel: "กึ")
Thai distinguishes between aspirated ("with a puff of air") and unaspirated ("without a puff of air") consonants. Unaspirated consonants exist in English too, but never alone: compare the sound of 'p' in "pot" (aspirated) and "spot" (unaspirated). Many English speakers find it helpful to pronounce an imperceptible little "m" in front to 'stop' the puff.
In Thai romanized with the Royal Thai General System (used on Wikitravel), the distinction is usually represented by writing aspirated consonants with "h" and unaspirated ones without it. In particular, "ph" represents a hard aspirated 'p' and not a soft 'f', and Phuket is thus pronounced "Poo-ket". Likewise, "th" is a hard aspirated 't' and hence Thailand is pronounced "Tie-land".
Other systems of romanization may use 'bp', 'dt' and 'g' for the unaspirated sounds, and 'p', 't', and 'k' for the aspirated sounds. This is not used in this guide.
like 'b' in "bed"
not used here, but in other romanizations may represent unaspirated 'p'
ch ฉ ช ฌ
like 'ch' in "chop"
d ฎ ด
like 'd' in "dog"
not used here, but in other romanizations may represent unaspirated 't'
f ฝ ฟ
like 'f' in "fun"
not used here, but in other romanizations may represent unaspirated 'k'
h ห ฮ
like 'h' in "help"
like 'j' or 'dg' in "judge"
like 'k' in "skate" (unaspirated)
kh ข ฃ ค ฅ ฆ
like 'c' in "Kate" (aspirated)
l ล ฦ ฬ
like 'l' in "love"
like 'm' in "mother"
n ณ น
like 'n' in "nice"
like 'ng' in "sing", but can also be used at the beginning of words
like 'p' in "spit" (unaspirated)
ph ผ พ ภ
like 'p' in "pit" (aspirated)
r ร ฤ
very light 'r', often pronounced as 'l' or omitted entirely
s ซ ศ ษ ส
like 'ss' in "hiss",
t ฏ ต
like 't' in "stop"
th ฐ ฑ ฒ ถ ท ธ
like 't' in "top"
not used here, but in other romanizations may represent 'w'
Basic Thai grammar is fairly straightforward. Word order is subject-verb-object, as in English. Nouns and verbs do not conjugate, and there are no plurals or grammatical gender. Instead, a wide array of particles and markers are employed to indicate past tense, negation, etc.
phom kin khao ผมกินข้าว
"I eat rice"
Adjectives are placed after the noun, not before.
phom kin khao suai ผมกินข้าวสวย
"I eat rice beautiful" (I eat white rice)
The negation marker ไม mai goes before the verb.
phom mai kin khao ผมไม่กินข้าว
"I not eat rice" (I will not eat/am not eating rice)
The past tense marker แล้ว laew goes after the verb and its object (if any).
phom kin khao laew ผมกินข้าวแล้ว
"I eat rice already" (I ate rice)
Pronouns are often omitted if it's clear from the context who is doing what.
Note that that the polite suffix ครับ khráp (for men) and ค่ะ khâ (for women) can and should be attached to all phrases when talking with strangers. The suffix depends solely on your gender. Also note that the pronoun for "I" is ผม phǒm for men and ดิฉัน di-chǎn for women.
When addressing people, คุณ khun is a safe, respectful all-purpose equivalent to "Mr/Ms/Mrs". People you're familiar with can be addressed as พี่ phii (if they are elders) or น้อง nong (if they are younger). These are always used with first names, so your business partner Supachai Sakulwattana is khun Supachai and your secretary Nipaporn Khampolsiri is nong Nipaporn. All Thais also have short nicknames, but these are only used informally.
The closer two friends are, the less often you will hear ครับ khráp and ค่ะ khâ being spoken. This is especially prominent in lower and middle classes, but is a general trend. This can be compared to western languages, where adding "Sir" at the end of each sentence when speaking to somebody in authority is becoming less and less common, and already entirely removed in many languages. On another note, there is a trend among the upper and middle classes, especially among younger men, to call each other phii, no matter the age difference. This is part of greater age equality in Thailand.
Mai pen rai
Many a visitor has suggested, perhaps slightly tongue in cheek, that ไม่เป็นไร mai pen rai should be the national motto of Thailand. Literally "is no problem", this is most commonly used where an English speaker would say "OK", "no problem" or "never mind". But watch out, as this can also be used in the negative sense: a mai pen rai in response to a complaint about missing your bus or being overcharged now means "it's not my problem" or "it shouldn't be a big deal for you".
When you're asking whether somewhere is far, the answers near/far are almost the same, but the tones are different. Klai means it's far, and Klâi means it's near, but people usually answer Mâi Klai (not far) instead. This is quite a difficult thing for travellers' ears.
Thai numbering is quite regular and speakers of Cantonese will find many quite familiar. Note that in casual speech it is common to drop the "sip" from numbers over twenty, eg. 23 is yii-saam instead of yii-sip-saam.
Thai has its own set of numerals, shown below, but these are used quite rarely — the major exception being sites with double pricing for Thais and foreigners, the Thai price being often disguised with Thai numbers. Being able to read the Thai price just might get you in at the Thai rate.
There are no less than three systems for telling time in Thailand. The easiest of the three is the 24-hour official clock, encountered primarily in bus and railway schedules. To create an official time, simply affix naalikaa นาฬิกา to the number of hours, so that e.g. kao naalikaa is 9AM (09:00) and sip-saam naalikaa is 1PM (13:00).
Things get a little more difficult in the 12-hour common clock. As in the West, the number of the hour runs from 1 to 12, but instead of just AM and PM, the day is divided into four sections (ตอน ton):
เช้า cháo (morning), from 6 AM to noon
บ่าย bàai (afternoon), from noon to 4 PM
เย็น yen (evening), from 4 PM to 6 PM
คืน khuen (night), from 6 PM to 11 PM
A 12-hour time is thus composed from the hour, the word mong โมง and the correct ton ตอน. As exceptions, the word bàai comes before mong (not after); 1PM is just bàai moong with no number; and there are special words for noon and midnight. Some examples: