Formal:
* ขอบคุณสำหรับความช่วยเหลือของคุณ (Khop khun samrap khwam chuai reuea khong khun) - This is the most formal way to say it, and it literally translates to "Thank you for your help."
* ขอขอบคุณสำหรับความช่วยเหลือ (Khor khop khun samrap khwam chuai reuea) - This is a slightly less formal way to say "Thank you for your help."
Informal:
* ขอบคุณสำหรับความช่วยเหลือ (Khop khun samrap khwam chuai reuea) - This is a more informal way to say "Thank you for your help."
* ขอบคุณนะ (Khop khun na) - This is a very casual way to say "Thank you," and can be used with friends or family.
* ขอบคุณมาก (Khop khun mak) - This is a more emphatic way to say "Thank you very much," and can be used in both formal and informal contexts.
Adding a little more nuance:
* You can add "มาก (mak)" to the end of any of these phrases to emphasize your gratitude. For example, "ขอบคุณสำหรับความช่วยเหลือของคุณมาก (Khop khun samrap khwam chuai reuea khong khun mak)" means "Thank you very much for your help."
* You can also use "สำหรับ (samrap)" before the specific act of help to be more specific. For example, "ขอบคุณสำหรับการช่วยฉัน搬运行李 (Khop khun samrap gar chuai chan ban yun sali)" means "Thank you for helping me carry my luggage."
Remember to adjust your tone and formality based on your relationship with the person you are thanking.