A multi system TV will work in Singapore. But you are pretty much out of luck if your TV are one of those entry level type with only one system built-in like a PAL or NTSC.
The only thing you can do with that is to playback LDs, VCDs and other video stuff that output the signal as NTSC. There are NTSC to PAL converters you could find at Sim LIm SQ if I recall correctly but usually the quality is pretty bad unless you are buying the higher end stuff but...it might be cheaper to buy a new TV especially if your present NTSC TV is a 21". A good converter will set you back a couple of hundred dollars upwards.
You are out of luck basically ..I think you can stop asking further but get a TV signal format converter that convert PAL to NTSC.
For your info ATSC is bascially what you would call digital TV systems that uses a video compression format(mpeg) that is more for digital broadcast but if you think that is usable in SIngapore....forget it for now. ...Singapore might go fully digital one day but there are right now about 18 ATSC formats! TO be sure anyone of them might be yours you also need to have a built in converter or buy one. Sell it to someone who might need a NTSC TV in the USA or Japan...etc. It is useless for watching Singapore TV or even cable tv. Unless as I said you want to watch movies from NTSC signal devices like vNTSC video, LDs, VCD and DVDs. Enough said...