EP's are tied to the employer who sponsored you. Leave them, lose your EP. Can you reapply? Yes, but while MOM doesn't really care, the new employer still has to justify the hiring of a foreigner, so even if you currently have an EP, that is still not a guarantee that you will receive another with a new company. They might not be able to justify or if on an S pass, they may not have the quota.
Having said all that, you shouldn't have a problem, but the possibility is always there. So leave your current employer at your own risk but remember, if you weren't retrenched, you've only yourself to blame.
SOME PEOPLE TRY TO TURN BACK THEIR ODOMETERS. NOT ME. I WANT PEOPLE TO KNOW WHY I LOOK THIS WAY. I'VE TRAVELED A LONG WAY, AND SOME OF THE ROADS WEREN'T PAVED. ~ Will Rogers