Work permit rejected / unsuccessful

You asked MoM directly and they replied that they only answer to your employer.
MoM knows MoM's procedures and thus you can assume the reply is correct.

I already ask for the employer to help me to ask for the reason. But they didn't reply me already. They already give me the letter of appointment. And ask me for working while waiting for the wp. But then things happen. My wp got rejected. So I go find another job, previously my position is sales. Then now I got a job as a waitress and still got rejected. I hope this time my current employer help me to find out why MoM always reject my application. If no, then idk how to settle this down if cannot go to their office. I really want to work at Singapore cause really can help my economic stable.

You should not agreed to work before your WP was approved. This is illeagal and the most likely cause of the rejections. You are Probably banned from working here for a number of years.
Don't do it again!

Thanks for the advise. It won't happen again. So my current employer ask for the reason of rejection of my wp, MoM said can't advice for the detail reason but this person is not suitable for work.  It's not like I have a bad record in Malaysia nor in Singapore before. I really don't understand why. 😔

When MoM said you are not suitable to work here, that means they have strong reservation on your application. Better you should work few years in your home country then try your luck again.