Thai swear words explained: know them, don't say them

Your cousins say something, everyone laughs, and you laugh too, half a second late. Or a TV drama hits a fight scene and the subtitles go suspiciously quiet. Knowing what those words mean is useful. Knowing why your mum’s face changed when you repeated one is even more useful.

This page explains the rude Thai you are most likely to hear, in plain English. It quotes only two rude Thai words, the rough pronouns. Everything else we describe instead of spelling out: the aim is to understand, not to add to anyone’s vocabulary.

Are ku and mueng rude?

Usually, yes. กู (guu) means “I” and มึง (mueng) means “you”. Wikipedia’s pronoun table for Thai marks both as “impolite/vulgar”, and Wiktionary labels them vulgar and offensive. You may see them romanized as ku and mueng; the Thai is the same.

They are not new slang. Wiktionary traces both back to Proto-Tai, and the Ramkhamhaeng inscription, which Wiktionary dates to 1292/93, has the king speaking of himself with กู (“my father is called…”). Over the centuries the words slid down the politeness ladder; Wiktionary now labels them vulgar.

What makes them confusing is that the same words do two jobs. As our Thai slang dictionary puts it, between very close friends they mean “we’re tight”. Said to anyone else, they are an insult. A 2022 study of pronoun use among Mae Fah Luang University students found both words in the students’ everyday repertoire, and found that the listener’s age was the most important factor in which pronoun someone chose, with closeness second. That is the whole rule in one line: who you’re talking to decides everything.

Why does it land so hard with elders?

Because in Thai, the pronoun is the relationship. Wikipedia notes that Thai pronouns are ranked by politeness and chosen according to the relative status of speaker and listener, and that people often use family words instead of “you” altogether. With Yai you don’t say “you”; you say ยาย (yaai). With an older cousin, พี่ (phii). Our guide to Thai family words has the full set.

So มึง to a grandparent isn’t just a rough word. It can come across as “you and I are equals, and I don’t need to be careful with you”, which is the opposite of what the family-word system is built to say. English has nothing quite like it. The nearest feeling might be calling your grandmother by a crude nickname at the dinner table.

That also explains a common heritage-speaker surprise: you can use a word you’ve heard a hundred times from cousins, and still get a sharp look from an aunt. The word didn’t change. The listener did.

What are the most common Thai rude words?

Thai Wikipedia’s article on rude words says taboo words usually refer to sex, excretion, death, animals or loss, and that insults mostly compare a person to something dirty. Most of what you’ll hear falls into a few groups. We describe them in English only.

• The rough pronouns. กู and มึง, above. Rude because of who they’re said to, not because of what they mean.
• Animal insults. Calling someone an animal is the classic Thai insult, and some animals are much worse than others (more below).
• Body and toilet words. Thai, like English, has crude words for body parts and bodily functions.
• Rough everyday verbs. Wikipedia’s overview of Thai registers mentions vulgar verbs for something as ordinary as “eat”. Whatever they mean among friends, at Yai’s table they are not funny.

Why is the monitor lizard insult so strong?

The water monitor is a large lizard you’ll see in Bangkok’s canals and parks. Its Thai name is also one of the strongest insults in everyday Thai. Linguist James Chamberlain, in a 2022 study of lizard words across Tai languages, calls it “an abusive term of the strongest order”. Wiktionary marks its insult senses “very offensive” and lists it as an exclamation of anger or disgust too.

Why this animal? There is no single proven answer, so be wary of anyone who gives you one. Chamberlain records that in Thailand and Cambodia the water monitor is “much feared and the subject of a number of superstitions”. If one swims in front of a boat, it is taken as an evil omen. Some people won’t say its name at all and use a polite stand-in that means “animal silver, animal gold”. As a possible reason, he quotes a zoologist’s note from the Philippines that the animal eats carrion. In most other Tai languages, he notes, these beliefs don’t exist.

Attitudes to the animal are softening. Wikipedia’s article on the species says Thai public perception of it has become more positive in the 2020s. The word, though, still hits hard. If you hear it, someone is usually very angry, or being deliberately crude.

What other animal insults will you hear?

Two everyday animals carry insults too, and neither is for family:

• The water buffalo. Wiktionary lists “stupid person, idiot” as a sense of the Thai word, marked very offensive. In formal speech even the animal gets a politer name.
• The dog. Used about a person or their behaviour, the word means low or bad. Again, polite speech has a separate word for the animal itself.

The pattern is useful to know: when someone is called an animal in anger, it is meant as an insult. Animal nicknames given with love, like Moo (pig), are a different thing entirely; see Thai nicknames explained.

What can you say instead?

You never need any of these words to sound close or natural. Thai already has softer tools, and they do the job better.

The polite endings do a lot of quiet work here. A plain sentence plus ครับ (khrap) or ค่ะ (kha) reads as warm and respectful to almost anyone older; see what ka and khrap mean. And if you want to sound relaxed with people your age without the rough pronouns, our essay on why your Thai sounds like your mum is about exactly that switch. The friendly slang lives in the slang dictionary linked above.

What if you said something rude by accident?

It happens, and it happens to a lot of people who learned Thai from cousins, TV or a school playground. A word sounds normal because you heard it every day, and only later do you find out what it is. That is how language works, not a failing.

Keep the repair small:

ขอโทษ

khor thot

Draft: waiting for a native speaker’s review.

Add ครับ or ค่ะ, and if you like, say in Thai or English that you picked it up from friends and didn’t know. There’s more on apologising to elders in our guide to sorry in Thai. Often the answer will be ไม่เป็นไร (mai pen rai), “it’s okay”. The Thailand Foundation describes the phrase as a way to calm tension and calls it “the gift of forgiveness”. Take the gift. Then, maybe, let an older cousin explain which of their words are for friends only.

If you are a parent and your child brings one of these words home, the same calm works. A quiet “that one is for friends, not for Yai” teaches the rule without making anyone feel bad for listening.

Reply Thai, coming soon to iPhone, has an optional Real talk section about the rude words close friends use, and when never to use them. It stays off until you turn it on in Profile.

Thai words on this page are a draft until a native speaker has reviewed them.