How do you write thank you in thai characters?

To write "thank you" in Thai, you use the phrase "ขอบคุณ" (pronounced "khob khun"). The characters are ข (kho), อ (o), บ (bo), ค (kho), and ณ (n). You can also say "ขอบคุณครับ" (khob khun krap) if you're male, or "ขอบคุณค่ะ" (khob khun kha) if you're female, to add politeness.