One of the major founding ethnicities of Singapore was overseas Chinese, who filled the same role anthropologists have long documented as Jews in Europe or Lebanese in Africa. It is unusual for subpopulations fulfilling that economic role to engage in petty crime (organized crime can be another story). And as the other poster mentions, the distinction between citizens and outsiders is about as severe as in GCC countries. So, the diversity of Singapore is somewhat less unrestrained than outsiders often depict.