Question words are very easy in Thai. Just like in English, you can ask just about anything with simply one or two words, making these very powerful and important vocabulary words to learn. There is one difference however from English, in that in Thai, the question word is usually (but not always) the last word of the sentence.

ไหน – nai 5, This can either mean ‘where’ or ‘which’.

ไปไหน? Where are you going?

ตอนไหน? When?

อันไหน? Which one?

คนไหน? Which person?

ที่ไหน? Where is it?

เมืองไทยอยู่ที่ไหน? Where is Thailand?

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อะไร – arai 1, This means ‘what’.

อะไร? What?

เป็นอะไร? What’s wrong?

อะไรเกิดคึ้น? What happened?

เรื่องอะไร? What is it about?

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เท่าไร – tow 3 rai 1, This means ‘how many’ or ‘how much’.

แพงเท่าไร? How expensive is it?

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เมื่อไหร่ – meu 3 rai 1, This means ‘when’.

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กี่ – gee 2, This means ‘how many’.

กี่บาท? How much baht?

กี่อัน? How many?

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หรือเปล่า – reu 5 blow 2, This means ‘or?’. There are many ways to ask ‘or?’ in Thai.

เหรอ? Really?

รึ? Or? (shortened spelling)

หรือ? Or? (official spelling)

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ใคร – krai 1, This means ‘who’.

ใครนี่? Who is this?

ใคร? Who?

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ทำไม – tum 1 mai 1, This means ‘why’.

มาทำไม? Why did you come?

วิ่งทำไม? Why did you run?

ทำไมไม่เอา? Why don’t you want it?

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ยังไง – yang 2 ngai 1, This means ‘how’ (spoken).

อย่างไร – yang 2 rai 1, This means ‘how’ (written).

มายังไง – How did/will you come?

ทำอย่างไรดี – What should we do? / How should I do it?

If you can handle the over exaggerated acting, here is a decent video with more examples: