This is the smallest set of Thai that changes how people treat you. Eleven of these phrases cover greeting someone, thanking them, apologising, agreeing, disagreeing and admitting you have not understood a word — which between them handle most short exchanges with a stranger.
Start with the politeness particles. They are the highest-value thing on the page and take about a minute.
The two words that make everything polite
Men use ครับ, women use ค่ะ, and the choice follows the speaker rather than the listener. Stick one on the end of anything below.
Becomes คะ, high tone, on a question.
Hello and goodbye
สวัสดี does both jobs and works at any hour. The time-of-day versions are correct but rarely used — learn them to recognise, not to say.
Final, and a little dramatic for leaving a shop.
Thank you and sorry
ขอโทษ covers "excuse me" as well as "sorry", and that is what you will use it for most — getting past someone, or starting a question to a stranger.
The reply to both of the above, and to most small problems.
Yes, no, and agreeing
Thai has no single word for "yes". ใช่ confirms that something is correct; ได้ agrees that something is possible. They are not interchangeable.
Borrowed, universally understood, and used constantly.
When you are lost in the conversation
The phrases learners skip and then need immediately. Saying you have not understood is not a failure — nodding through an exchange you have not followed is.
The particle does more work than the phrase
If you learn nothing else here, learn ครับ and ค่ะ. They attach to the end of almost any sentence and turn it from blunt into polite, and they cost one syllable.
The rule that trips people up: you choose the particle by your own gender, not by who you are talking to. A man says ครับ to everybody — his boss, his wife, a child. A woman says ค่ะ to everybody. It does not switch.
Women have one extra thing to know. On statements it is ค่ะ with a falling tone; on questions it becomes คะ with a high tone. Men use ครับ for both. You will absorb this by ear long before the rule feels natural.
Do not wai everyone
The palms-together ไหว้ is genuinely complicated — hand height, who goes first, who returns it — and visitors usually respond by doing it to everybody, which is the one clearly wrong answer.
You do not wai children, or staff serving you, or the person taking your money. Return a wai when an adult gives you one, offer one to someone clearly senior, and the rest of the time a nod with the spoken greeting is completely correct.
Say when you have not understood
The most useful phrase on this page after the greeting itself is ไม่เข้าใจ, "I don't understand". Learners avoid it because it feels like an admission of failure, and then nod through an entire exchange they have not followed.
Pair it with พูดช้าๆ, "speak slowly". Both are received well — someone who says "I did not understand, could you slow down" in Thai has still done the thing, and the conversation usually gets easier from there rather than harder.
Common questions
What is the difference between krap and ka?
Nothing except who is speaking. Men say krap, women say ka. Both are politeness particles added to the end of a sentence, they carry no meaning of their own, and the choice is made by the speaker's gender rather than the listener's.
How do you say hello in Thai?
สวัสดี, sà-wàt-dii, with krap or ka on the end. The same word serves as goodbye, and it works at any time of day.
Do I need to wai when greeting someone?
Not usually. Return a wai if an adult offers you one, and offer one to someone clearly senior to you. Do not wai children or service staff — a visitor wai-ing everybody is a common mistake rather than good manners.
How do you say yes in Thai?
There is no single word. ใช่ (châi) confirms that a statement is correct, and ได้ (dâi) agrees that something is possible or permitted. Answering a "can you" question with châi is a very common beginner error.
Is it rude not to say krap or ka?
Not rude exactly, but noticeably blunt — roughly the way saying "yeah" lands when "yes please" was expected. It costs one syllable and it is the cheapest way to sound like someone who has made an effort.