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, Altel, and Unifi.
Although Yes is completely 4G/LTE, Altel and Unifi have a 2G and 3G roaming agreement with Celcom, so their customers do not have to worry about no 4G/LTE coverage in some places.
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. If you cannot click on the image, then the review of the operator is on its way – stay tuned!