Gangsters are ultimately cowards, hence moving in a group. Back when I was in secondary school, I had one class where at least half the guys are from gangs. Most from the same gang, too. I had my fair share of fighting, though. Kinda enjoyed beating people up.
But its good that they didn't like cut you up, or spill acid over you like those Malaysian road tugs. But I really do hope they are caught. Feel for ya. Beefing up is one way to make things a little easier, you might turn out stronger than your attacker. Personally I am quite a fitness freak because of how dangerous its become, simply walking around alone at night.
And let's not mention too much on race, after all, we're all Singaporeans, that's our identity.