Yeah, but Israel is also tiny and can still kick the ass of everyone else in the Middle East. Similar to Israel, Singapore has a lot going for it with respect to modern warfare that makes up for its population and landmass deficit. I agree that total invasion is probably very unlikely in the foreseeable immediate future.
You are off by quite a bit there. Besides, whether you are willing to admit it or not, a LARGE part of the Israeli swagger is the understanding that they have the full might of the US army behind them (be it right or not). Singapore does not have an equivalent relationship.