Bangkok Suvarnabhumi

Suvarnabhumi (sue-wanna-poom) Bangkok International Airport is the principal gateway into Thailand for air travellers. Opened in October 2006, Suvarnabhumi (BKK) replaced the old Don Muang Airport (DMK) as Thailand’s major aviation hub. Don Muang still serves as a domestic airport and cargo centre.
The guide below for passenger movements comes directly from Airports of Thailand (AOT)
Arriving passengers
Enter the passenger terminal via the 2nd floor of the concourse building except bus gate passengers. At the terminal, there are passport control checkpoints where passenegers can collect their baggage from one of the 22 baggage conveyor belts, 17 of which are for international passengers and 5 are for domestic passengers. Once passengers have collected their baggage and passed the customs control checkpoints, they can proceed to the arrivals hall where they will find transportation counters, hotel and accommodation counters and a tourist information centre.
Outside the arrivals hall are pick-up points; in the case of passengers travelling with a tour agency, they must proceed to the 1st floor for buses and coaches. There is a meeting point on 3rd floor.

Transit/transfer passengers
Go to the airside area after they arrive at the 2nd floor of the concourse building from the aircraft in order to proceed with the transfer process before continuing to 3rd and 4th floors to complete departure procedures. In the case of transit passengers, they will have to go through the airside area to the departures service area in order to complete the departure procedures.
A video tour of Bangkok Suvarnabhumi International Airport