1. For a starter, it will be easier to use local platform to trade due to logistic to open account, although the transaction cost is more expensive to trade SGX in malaysia platform (brokerage MBB 0.4%, CIMB 0.42%, plus some bank charges)
2. When you already have the local platform, and if you plan to trade on SGX on a larger scale, then ask your malaysian broker to open a Sg platform for you. The transaction cost is 0.18% (for 1 to 1 cash trade) up to 0.275%-0.28% (for T+5)
3. If you are big traders, of course go for Sg broker. If you are a small timer, the difference in brokerage is not much. You can estimate the difference in brokerage cost with the above mentioned brokerage rate