I think you should purchase separate SIM since your visit is more to Malaysia than neighbouring countries.
For Malaysia eSIM, I would suggest TuneTalk as it rides on Celcom network which will provide you decent coverage throughout Malaysia.
https://www.tunetalk.com/prepaid-purchase/s...ew_number/1610/

For neighboring countries, do check out Hello1010 https://hello1010.my/ as they have wide range of travel SIMs.