I’m facing same situation.
I have work permit and I applied for full time study.
Immigration officer said you need to go back first and then you can apply for student visa.
But if you want to do diploma maybe can part time.
Part time can I think
Work Permit holders are required to refer to the Immigration Department directly for further details on the procedure to study in Malaysia. Kindly note that EMGS only processes applications for international students enrolling to study full-time in Malaysia.