If you have read my Buying a SIM Card in Malaysia Guide, then you know that Malaysia has 4 main operators: Digi, Maxis/Hotlink, Celcom, and U Mobile. Additionally, the country has 3 4G/LTE-only operators, which are Yes 4G, Altel, and Unifi.
Finally, there are plenty of Malaysian Mobile Virtual Network Operators (MVNOs), so you have a lot of choices in SIM cards when visiting Malaysia.
Not getting a Malaysian SIM card when exploring Malaysia would be a disservice to yourself. Get one – they are cheap. Click on any of the logos to read my review of the said operator.