Singapore is actually smaller than New York City. I wonder where they keep all those tanks.
Don’t know about the tanks as such but a lot of their air force assets are based/deployed to Australia, France (mainly training) and of course the US. While their navy frequently deploys to Australia and India for training.
http://xbradtc.com/2013/04/09/mountain-home-afb-home-of-the-singapore-air-force/
In addition, most people who visit NYC think only of Manhattan or possibly the area between the three major airports and Manhattan with multi-story buildings. Most of Staten Island and the outer boroughs have large tracts of single family homes with nice, albeit not spacious yards.
Only about one third of Singapore's area is densely settled. The remaining two thirds consists of industrial parks, nature preserves, small towns with tract homes and minimal yards and, yes, military bases. It is about a 20 minute train ride and a slightly longer bus ride from downtown Singapore to Johore Baru, the first town across the straight in Malaysia. Most of that trip takes you through relatively sparsely settled areas as described. The locals will even point out the military bases for you if you ask them politely because the chances are pretty good that they've done reserve duty there.
I expect if a neighbor invades, Singapore will suddenly increase its land area by an order of magnitude - which isn't difficult given that the country's only a couple of hundred square miles. That will give its tanks something to do.