Seletar Airport Departures
Leaving Singapore through Seletar is quite easy. There is only one terminal, with one check-in counter. The counter is generally only open a couple hours before each flight, but if you come early there's a fairly comfortable air conditioned waiting room.
When checking in, you first need to pass your checked luggage through the scanner. After getting your boarding pass, you may need to wait until the departure lounge is open. To get to the departure lounge, you now need to pass your carry-on bags through the X-ray scanner. Then you proceed to passport control, through a security screening, and out of the terminal building to reach the departure lounge.