[eric-the-viking]

when you leave phuket to go bkk as long as your not checked in as a transfer passenger ,you will not pay the departure tax untill bkk international.
as safeas says you have to collect your baggage at the domestic arrivals then you do the walk of shame across the bridge ,through the car park and up the lift to the international departure where you check in again with your respected carrier,as you go through customs you pay your 500bht departure tax at the little window kiosk then go through passport control and customs.