Formal:
* ขอบคุณมาก (khɔ̂ɔp khun mâːk) - This is the most common and polite way to say "thank you very much."
* ขอบคุณสำหรับ... (khɔ̂ɔp khun sǎm-rǎp...) - This means "Thank you for..." and you can add the specific thing you are grateful for after the "for." For example: "ขอบคุณสำหรับความช่วยเหลือ (khɔ̂ɔp khun sǎm-rǎp kwǎːm chûaj-lɯ̌a)" which means "Thank you for your help."
Informal:
* ขอบคุณ (khɔ̂ɔp khun) - This is a shorter, more casual way to say "thank you."
* ขอบคุณนะ (khɔ̂ɔp khun ná) - This is another informal way to say "thank you," with a friendly tone.
Other options:
* ขอขอบคุณ (khɔ̌ɔ khɔ̂ɔp khun) - This is a more formal and respectful way to say "thank you."
* รู้สึกขอบคุณ (rûː sɯ̌ːk khɔ̂ɔp khun) - This literally means "feel grateful" and is a more emotional way to express appreciation.
The best way to choose the right phrase depends on your relationship with the person you are speaking to and the situation.