Formal:
* เพื่อน (pʉan) - This is the most common and general way to say "friend."
* มิตร (mit) - This is a more formal and literary way to say "friend," often used in writing or speeches.
Informal:
* เพื่อน (pʉan) - This is the same word as the formal version, but pronounced with a shorter vowel sound.
* เพื่อนรัก (pʉan rak) - This means "close friend" or "best friend."
* พี่ (pii) - This literally means "older sibling" but can also be used to address a close friend, especially an older one.
* น้อง (nɔ́ŋ) - This literally means "younger sibling" but can also be used to address a close friend, especially a younger one.
The best way to say "friend" in Thai will depend on the situation and your relationship with the person you are talking to.