Singapore is the cradle of climatic tedium of boiling temperature and dripping humidity.but the worst is the freezing conditions of indoors created by all the airconditioners that drone on full blast. So you have to oscillate between two extreme temperate zones in the little island . The only thing I can suggest is that every morning you should first think about whether you are going to spend more time in or out. If in, then wear a suit and tie. But if are out most of the time , it might be more suitable for you to dress casually.