This article seems to detail the legal position: https://www.thestar.com.my/news/nati...-holders-told/

Otherwise most of the posts in this thread are along the right lines - people operate under a don't ask don't tell policy,

Theoretically someone could analyse your passport stamps, but think about the average day in the life of a low-level government employee processing passport renewals, who can be bothered unless there is a specific directive or reward from higher up?

I know several Malaysians living in Australia who have become citizens but still keep and renew their Malaysian passports, but they go back to Malaysia frequently.

I have heard of spot checks by Imigresen at boarding gates in KUL - here you need to show your non-Malaysian passport! (This is just a visual check from what I have heard)

China (PRC) is a different case - if a government official discovers you have multiple passports, even by accident, they will force you to make a decision on the spot.