I was from NCS in managerial position.

If what you have applied for is a senior position as a specialist, not a programmer, and not a PM, then S$4K+ is the reasonable expectation. If you do well as contract, you'll have a chance to be converted to permanent staff after 1 year.

But as previous poster has mentioned, you have to ask whether you will be working from client's place or from NCSHub, because working at client's place means less benefits and it will also be difficult for you to nail down your lodging location. You'll also have to content with reporting to the client's PM in addition to your own (a nightmare).