@vinsan,
Wow. That's a toughie, but it sounds more like a judgement call rather than selfishness.
I don't even know what I would do, but I'm guessing that I would give serious thought to staying in Singapore if the new deal gets you into permanent status, if she could and would be with you then, if the new salary isn't eaten up by living costs in Singapore, and if you actually enjoy living there.
Anyway, I would vote for longterm security and happiness, but neither is really predictable and happiness is subjective. Ask your wife. Wives know about stuff like this.