Are you on one itinerary or two?

If one, then it's a simple question of whether you've got a valid connection. It's international to international, so you would not need to clear immigration and would obtain your onward boarding pass in SIN. BKK is a pretty good airport and, even if you had to get from one extremity to the other, I would have thought you would be OK.

If two itineraries, then I would say it's not enough time (especially if you have to clear immigration). You should be able to check your luggage all the way through, however.