IPA Withdrawal Stay With Current Employer

As long as the new EP is not issued (or the old one cancelled for other reasons), your old EP remains valid.

BUT:
- You have a valid employment contract with company B. Do by all means keep the termination rules (incl. notice period) or find a mutual agreement with them, otherwise they can lodge a complaint with MoM, which might get both your EPs cancelled!
- Changing your mind in such a way is bad in the eyes of MoM, so your next workpass application has less chances of approval. Better do not change job again for at least a few years!
- And of course company A will see, in MoM's system, that a new EP was applied for (but not by which employer). Such illoyal employees are often first if somedody needs to be laid off.

Not an easy decision - but you have only yourself to blame!

@beppi - I don’t agree with few points here -

I never had problems with MOM bcoz or frequent job changes. I changed job within 10 days of joining and my EP was approved in a week. So not sure if job hopping is discouraged by MOM.

Avi: MoM works by its own, unpublished rules and my understanding is based on a limited number of stories I read on this forum and other sources, which I interpret in my own way - so what I write may be not or at least not always applicable.
In my understanding, job-hoppers are not preferred, but the negative implication is less strong than some other aspects (like e.g. job skills and how urgently Singapore needs them). Generally, one job change is accepted - even MoM seems to understand that you can make a mistake once - but many in short succession are not.
However, and more relevant to the OP, MoM seems to dislike people who change their mind even before starting the new job - thus wasting time and effort of the MoM officers and the new employer.
Again, this is probably not a killer criterium and Nobel prize winners or world athletes can probably get away with a lot more job-related dithering than us normal folks.
AND: MoM is also open to reasonable explanations as to why a situation arised. But will the OP or his wanna-be employer submit an convincing explanation with the cancellation?