hope to come singapore

Dear Nguyen,

Welcome to the forum.
Accommodation is on the top of the mind for many expats coming to Singapore. But if you have sufficient money (as Singapore rentals are not cheap - if you don't have at least S$1000/month for a sublet room or S$3000/month for an apartment, don't come!), it is no problem to find a reasonable place within a short time. So you only need to arrange for temporary accommodation (hotel, hostel or serviced apartment) for a few weeks and start flat-hunting!
There will be many real estate agents offering their services (for a fee, of course) and you might want to engage one if you are in a hurry (i.e. have two weeks or less to find a place), but it is also perfectly doable without them, it will just take a bit more effort and time. Please also note that Singapore housing agents have a bad reputation with regards to honesty and quality of service, so be careful when you engage one!
Good luck!