I think every time I've flown into SIN late at night, I've reached my hotel in less than an hour from the time the plane pulls up to the gate.

At SIN, SQ allows very early check in, up to 48 hours in advance with baggage, if you really want. But it may be smarter to just leave the bags at your hotel and do some eating or drinking downtown, then head out the airport closer to flight time.

Charles