I know that usually departure tax is included in flight tickets, but not always.
A guy in my hostel here in Bangkok says he has had to pay at the airport in both Vietnam and Indonesia. I once had to pay an unexpected "airport improvement tax" at the airport when leaving Canada, which amounted to the same thing even though it wasn't officially a "departure tax".
So when taking an international flight out of Thailand is there a departure tax or any other tax or fee which must be paid at the airport?