From the perspective of linguistic typology, Thai can be considered an analytic language. The word order is subject–verb–object, although the subject is often omitted. Thai pronouns are selected according to the gender and relative status of the speaker and the audience.
Thai has several registers, each having certain usages, such as colloquial, formal, literary, and poetic. Thus, the word "eat" can be กิน (kin; common), แดก (daek; vulgar), ยัด (yat; vulgar), บริโภค (boriphok; formal), รับประทาน (rapprathan; formal), ฉัน (chan; religious), or เสวย (sawoei; royal).
Nouns in Thai are uninflected and have no gender; there are no articles.
Thai nouns are neither singular nor plural. Some specific nouns are reduplicated to form collectives: เด็ก (dek, child) is often repeated as เด็ก ๆ (dek dek) to refer to a group of children.
The word พวก (phuak) may be used as a prefix of a noun or pronoun as a collective to pluralize or emphasize the following word.
Plurals are expressed by adding classifiers, used as measure words, in the form of noun-number-classifier (ครูห้าคน, "teacher five person" for "five teachers").
While in English, such classifiers are usually absent ("four chairs") or optional ("two bottles of beer" or "two beers"), a classifier is almost always used in Thai (hence "chair four item" and "beer two bottle").
Possession in Thai is indicated by adding the word "khong" in front of the noun or pronoun, but it may often be omitted. For example:
ลูกของแม่ (luk khong mae) - "child belonging to mother" - mother's child
นาอา (na a) - "field uncle" - uncle's field
There is no morphological distinction between adverbs and adjectives. Many words can be used in either function. They follow the word they modify, which may be a noun, verb, or another adjective or adverb.
คนอ้วน (khon uan) - a fat person
คนที่อ้วนเร็ว (khon thi uan reo) - a person who became fat quickly
In Thai, subject pronouns are often omitted.
The reflexive pronoun is ตัวเอง (tua eng), which can mean any of: myself, yourself, ourselves, himself, herself, themselves. This can be mixed with another pronoun to create an intensive pronoun, such as ตัวผมเอง (tua phom eng - I myself) or ตัวคุณเอง (tua khun eng - you yourself).
Thai also does not have a separate possessive pronoun. Instead, possession is indicated by the particle ของ (khong). For example, "my mother" is แม่ของผม (mae khong phom - mother of I).
Verbs do not inflect. They do not change with person, tense, voice, mood, or number; nor are there any participles.
ฉันตีเขา (chan ti khao) - I hit him.
เขาตีฉัน (khao ti chan) - He hit me.
The passive voice is indicated by the insertion of ถูก (thuk) before the verb. For example:
เขาถูกตี (khao thuk ti) - He is hit.
Tense is conveyed by tense markers before or after the verb.
Present can be indicated by กำลัง (kamlang, currently) before the verb for ongoing action (like English -ing form), by อยู่ (yu) after the verb, or by both. For example:
เขากำลังวิ่ง (khao kamlang wing), or
เขาวิ่งอยู่ (khao wing yu), or
เขากำลังวิ่งอยู่ (khao kamlang wing yu) - He is running.
Future can be indicated by จะ (cha, "will") before the verb or by a time expression indicating the future. For example:
เขาจะวิ่ง (khao cha wing) - He will run or He is going to run.
Past can be indicated by ได้ (dai, "did") before the verb or by a time expression indicating the past. However, แล้ว (laeo, already) is often used to indicate the past tense by being placed behind the verb. Or, both ได้ and แล้ว are put together to form the past tense expression. For example:
เขาได้กิน (khao dai kin) - He ate.
เขากินแล้ว (khao kin laeo) - He has eaten.
เขาได้กินแล้ว (khao dai kin laeo) - He's already eaten.
Tense markers are not required.
Thai exhibits serial verb constructions, where verbs are strung together. Some word combinations are common and may be considered set phrases.
เขาไปกินข้าว (khao pai kin khao) - He went out to eat, literally He go eat rice.
The particles are often untranslatable words added to the end of a sentence to indicate respect, a request, encouragement or other moods (similar to the use of intonation in English), as well as varying the level of formality.
They are not used in written Thai. The most common particles indicating respect are ครับ (khrap, with a high tone) when the speaker is male, and ค่ะ (kha, with a falling tone) when the speaker is female.
Some of the common Thai prepositions are: เกี่ยวกับ (gìeow gàp), ที่ (têe), สำหรับ (săm-ràp), ใน (nai), ของ (kŏng), ไปยัง (bpai yang), ด้วย (dûay).
This is a very brief overview of Thai grammar. To truly master it, you will need to study each of the aspects in much more detail. However, this overview will hopefully give you a general idea of the Thai grammatical system and of the main points you should consider when learning.