Both local and foreign workers in Singapore are protected from excessive working hours under the Employment Act (EA). They should not be contractually required to work more than 8 hours in a day or 44 hours in a week. ... Even when such exemptions are granted, employers should not compel employees to work overtime.

Go read up employment act. I suggest you to know your rights.
Record evidence. Email whatapps message if your boss force you to work overtime and no overtime pay...

Don't be dumb ass like this people here who act overtime as norm.