Car rental agencies rarely ask for anything other than your proper licence, including in Malaysia.

In my experience it's typically just law enforcement who might ask for the IDP if they are uncertain of what your licence is telling them in terms of your entitlement to drive, and quite often that can be a personal officer decision based on their grasp of English (or any other language). I have had to show an IDP a few times including one in Sarawak, but it has always been at roadblocks on very rural roads and quite a few years ago now.

If you have got the chance to get an IDP it's useful to have but is rarely asked for.