singapore will only be hit by a tsunami if
1) the epicenter of the quake is near the nicobar islands, or north of the epicenter that hit indonesia last december
2) that earthquake is about at least 7 on the richter scale to cause a small one...and about 9 to cause the one that hit last year.
3) and even if singapore gets hit, it would be a pretty high wave but not a powerful one bcause the johor straits is narrow and would cut out the force, only problem is the height of the waters will increase
if it happens, it happens, dont panic unneccesarily and worry yourself.