Though many other aspects of Thai grammar are quite simple compared to other languages, that certainly doesn't apply to its complex and involved personal pronoun structure. Whereas a learner can get by to start with by learning just a few of the more common ones, a native Thai speaker may switch personal pronouns many times a day depending on the situation and who they're talking to. The variety of pronouns range from the very formal to the very casual/insulting, and there's distinct differences between male and female usage. An additional difficulty is that several of the pronouns have more than one meaning, and you may need to use the context to work out the true meaning.
Making things slightly easier is the fact that subject pronouns and object pronouns are the same (there's no difference between 'I' and 'me' in Thai for instance) and that personal pronouns are frequently omitted from sentences altogether if they can be implied from the context. Despite its initial difficulty, once you get used to the Thai system of personal pronouns it can be very useful as it can tell you a great deal about the relationship between the speakers, the type of situation and often indicate relative age differences too.
Polite Personal Pronouns
The standard polite personal pronouns are:
I / me (only used by men)
| เขา kăo
He / him / she / her
If you're just beginning to learn, then it's safe to use just these words and you'll never offend anybody. pŏm and kun are somewhat formal words though, and as such may sound a bit out of place in casual and informal situations. kăo , man , rao and pûak kăo are commonly used both in polite and informal speech. For "they / them", the pûak is really only necessary if without it the context would be unclear, otherwise "they / them" can be translated just as kăo the same as "he / she".
For women, chăn can be used in both polite and informal situations. Men also sometimes say chăn , mostly when chatting with close friends or to their girlfriend or wife, but it's a fair bit less common. A man saying chăn excessively often or in inappropriate situations risks sounding somewhat effeminate too, so it's best used with caution.
Informal Personal Pronouns
| เรา rao
I / me
You (used by men and women, but only to refer to men)
| เธอ ter
You ; She
She ; You ( to refer to women)
ter is an informal pronoun meaning 'you'. It's most commonly used when speaking male <> female, and is much less often encountered in same-sex conversations. It's also mainly only used when talking to someone of a similar age to you. chăn and ter are the pronouns of choice for the majority of Thai pop songs, regardless of whether it's a man or woman singing. As an alternative to ter when talking to men, either men or women can also use the similarly informal naai to mean 'you'.
ter also has a less common meaning of 'she/her'. It's a more formal word when used in this context, and occurs mostly in written Thai.
rao , the standard word for 'we / us', is confusingly enough also informally used as a pronoun for 'I/me' too. It's mainly men who use it this way (as women have the alternative chăn ), and it's frequently partnered with ter or naai for 'you'. When rao is intended to mean 'we/us', the sentence will often also contain the word กัน ( gan , meaning "together") to make the meaning clear.
lòn means "she", or less commonly "you", and is predominately used in written Thai. If used in spoken Thai, it can have something of a sarcastic or mildly derogatory connotation and so is best used with caution.
I / me
ตัวเอง dtua ayng
ai 'I/me' and yoo 'you' are relatively recent additions that have been taken straight from their English equivalents, no doubt much to the chagrin of language purists. Another pairing, เค้า káo 'I/me' and ตัวเอง dtua ayng 'you' is used similarly in casual situations. Both are most common amongst students and teenagers, and rarely used by those much older.
The use of káo and dtua ayng can be very confusing if you're not expecting it, given that เค้า often sounds identical to เขา kăo ( the word for "he/she" as above) and the standard meaning of ตัวเอง dtua ayng as 'one's self'.
Very Informal / Offensive Pronouns
I / me
He / him / she / her
You ; He/She
goo , 'I/me' , meung , 'you' and man , 'he/him/she/her' (though literally 'it' as above) are often used by friends of many years when talking amongst and about each other. Used this way they serve as a kind of bonding term that shows close friendship, but be warned that using these terms outside of with close friends is considered very impolite and potentially abusive. As such they can cause considerable offence if used inappropriately, and unless you're very sure of your ground you're best off avoiding using them altogether. gae and eng , both meaning 'you', are similar to meung although marginally less impolite.
gae also has limited use as a third person pronoun too. When used this way, it's not at all impolite but is used to refer in a respectful way to elders. Thai people referring to their parents in the third person will often use gae for instance.
I / me (only used by men)
I / me (only used by women)
I / me
Of these, you're most likely to encounter tâan as it's commonly used by business when referring to customers in a general way. grà-pŏm or dì-chăn can be partnered with tâan and used in very formal situations or where you want to be extra-polite. You're very unlikely to ever hear the even more formal kâa-pá-jâo in normal speech, but may encounter it sometimes in official and formal documents (such as the Immigration form you fill in when entering Thailand).
PluralsIn the "Polite Personal Pronouns" section above, you can see kăo as the word for "he / him / she / her" and pûak kăo for "they / them". The word พวก pûak ( "group") can actually be added in front of any of the other pronouns to make them plural as needed, so for instance you could say พวกผม pûak pŏm for "us" or พวกท่าน pûak tâan for "you" (in a plural sense).
Nicknames and TitlesIn casual speech, it's very common for women to avoid using a first-person pronoun altogether and instead refer to themselves in the 3rd person by using their nickname. For instance, someone called เหมียว mĭeow (usually written as "Meow" ) would say the equivalent of "Meow is tired" rather than "I am tired". Similarly, they can also be referred to using their nickname instead of a second-person or third-person pronoun (e.g. "Is Meow tired?" rather than "Are you tired?"). Though this may take a bit of getting used to at first, it's a useful way of addressing someone if you're not sure which of the various pronouns is most appropriate.
While it's not unknown for men to also refer to themselves this way on occasion, it's much less common and, as with using chăn , may sound quite effeminate unless you're sure of your ground.
When addressing someone who has or works in a respected position, it's usually respectful and appropriate to use their title rather than any of the above pronouns. So students will refer to their teacher as อาจารย์ aa-jaan (the word for "teacher") and patients or staff to their doctor as คุณหมอ kun mŏr (the word for "doctor").