Singapore's crime rate

Lucky Tan asked:

Singapore has the highest prison population per capita after USA among developed countries. We have the 2nd highest rate of incarceration in South East Asia. Our rate of imprisonment is triple that of Malaysia. There is this poster that the SPF put up around housing estates that says "Low Crime Rate Does not mean no crime". If our crime rate is low, why are there so many people imprisoned? The USA has a large prison population because the crime rate is high.
http://singaporemind.blogspot.com/2011/11/singapores-high-prison-population.html