Email Pos Malaysia.

The same thing happens for my registered parcels from Hong Kong, so what I do is that after tracking with Hong Kong Post to verify my parcel has been sent out, after a 2 days (usually 1 day is enough for my parcel to reach MY soil) I will email Pos Malaysia at csc@pos.com.my.

My email will say something like I've a parcel from HK, tracking number XXXX, please email me the assigned Malaysian tracking number, thanks.