Formal:
* สบายดีไหม (sabai di mai) - This is the most common and polite way to ask "how are you?"
* คุณสบายดีไหม (khun sabai di mai) - This is similar to the above, but adds the honorific "khun" (you) and is more formal.
Informal:
* เป็นยังไงบ้าง (pen yang ngai baang) - This is a more casual way to ask "how are you?"
* สบายดีมั้ย (sabai di mai) - This is a more informal way of asking "how are you?" and is often used with friends or family.
You can also use these expressions:
* ร่างกายแข็งแรงดีไหม (raang gai kaeng raeng di mai) - This literally translates to "is your body strong?" and is a polite way to inquire about someone's health.
* อะไรบ้าง (arae baang) - This literally means "what (is there)?" and is a casual way to ask "what's up?"
The best way to choose the appropriate expression depends on the situation and your relationship with the person you are speaking to.