Whenever i've flown to Singapore the limit baggage wise was either 25kg or 20kg depending on the airline , these bags are always weighed automatically as they put them on the conveyor belt and you have to pay excess baggage if they are to heavy , I nearly got stuck in Indonesia once when they weighed my suitcase and wanted 550,000idr excess baggage charge hhehe i was lucky i had 556,000idr on me and they wouldnt take credit card or sterling! , hand luggage varies also but cdstg is right its usually 6-8kg although i've never had it weighed and once it must of been 15kg+ minimum (i put all the heavy stuff in it) , if you are worryed about excess baggage charges you can get small luggage scales (like a fishing type with a dial and hook , might be worth considering)
Hope that helps Scottish Rob