Hi 40k,
Some people with 2-3 bedrooms (condo unit) share the rent with their friends so they need not carry the burden of paying the entire unit-rent. If the monthly rental fee is around S$1.5k then a bedroom-occupant only pays S$500. So if you have friends here try to ask help from them. Electricity, water, others reserve a S$100
Food are not so expensive but better yet buy a-week supply and cook/eat at home.
You can go out shopping on weekends, there are a lot of stores offering On-sale goods. Or save your money first then buy the better stuffs after several months.
Nightlife (or likes) , you can still do it once or 2x a month. Just have a fixed budget for that, do not overspend.
40k/year is a good start...