Departing From Bangkok's Don Muang Airport
Check-in for departing flights from Don Muang Airport is on the third floor. Note that you'll need to scan your baggage to be checked (but not your carry-on) before you can reach the check-in counters.
After checking-in, domestic passengers go through a single security scan to get into the departure lounge, which has a large variety of food and shopping facilities. Don't forget that you will need to have your passport ready to show at the gate.
International passengers will go through immigration and then a security scan to get to the international departures area. The departure area has a fully stocked duty free shop as well as several restaurants and shops.