If you go through passport control in another airport (Samui, Chiangmai, Phuket, etc), as Ellie says you are already stamped out of Thailand. In Bangkok you are a CIQ passenger and must go directly to your gate.
Isn’t a Time Deposit the same as a Fixed Account? I have a one-year fixed account but I’m able to deposit and withdraw at any time. It just resets the interest calculation. So there shouldn’t be an exception.