There is also a good kopitiam (food court) in the B2 level of T3 (landside) and I'm pretty sure it's open 24 hours. The Taiwanese stall is especially good but you can also get a variety of Singaporean classics there. Because of the way Changi is set up you will need to re-clear security anyway to catch your outgoing flight, so no harm in going landside.
I'd encourage you to get out of the airport though, Changi is simple to navigate and cabs in Singapore are easy to deal with.