Singapore expats, can you give me advice regarding my employment, please?

I'm an engineer and I've been working in JB, Malaysia for 1 year & 9mos, with an Employment P to expire on February 2009..I tried to find a job in Singapore because I want to focus my career there due to safe and convenient to stay.The Singapore company selected me and they apply an Employment p for me. After 1week they informed me that my E-P is already approved by MOM and I need to go for medical. I submit a resignation to my company on the 10th, effective on the 31st. I already finished my medical. My problem now is, what if my employment p in Malaysia is not cancelled yet because it takes time for the cancellation, is there any problem with the MOM upon submission of my doents? Is it illegal? Will they reject my application since I still have permit in Malaysia? My plan is to work in Singapore and cancel my Malaysia EP later on. It's really a big problem to me..Thanks for your advice...