My 2 cents worth. I am from the oil gas industry.

From what i am aware of, you should be asking the same as what you were getting in malaysia, not taking the currency exchange into account. So if you were getting 4k ringgit, ball park will be 4k SGD.

Kudos to you if you can get a project manager position with your age and experience esp with the MNC but i seriously doubt so. The average pay for a PM in say shell,exxon should be min 150k PA above. But those dudes have at least 20 freaking years with plenty of high profile projects under their belt.

btw, petrochemical and oil/gas are 2 different ball games. Big diff in pay scale. $4k will be able right for petrochemical.