From another thread:
I think I have heard a Cantonese speaker try to get the attention of a waiter, using "m goi". Did I hear correctly?vince said:謝謝 (xie xie) is Standard Chinese/Mandarin, you cannot say that in Cantonese. If you want to say "Thank you", you must say 唔該 (m goi) in return for favors.
If you receive a gift, you say 多謝 (do ze). Mandarin and English do not have this distinction.