You are saying fsmone has the lowest commission?
Assuming you have 15K SGD to invest.
Let us ignore the exchange fee (which is to be paid to SGX in this case).
Base on FSMOne fee structure, you will only pay 8.80 SGD
https://secure.fundsupermart.com/fsm/new-to-fsm/pricing-structure -Select Stocks
Assuming you are looking at Moomoo or Tiger, there are 2 fees you have to pay, both Comission and Platform Fee. Both are 0.03% * Trade Value
Let us also ignore the exchange fee (which is to be paid to SGX in this case).
Comission: 15,000 * 0.03% = 4.5 SGD
Platform fee: 15,000 * 0.03% = 4.5 SGD
https://www.itiger.com/sg/commissions#singapore_stocks
https://www.moomoo.com/sg/broker-about/pricing - Select SG and click More
Higher buy in amount, FSMOne has the advantage due to fixed fees
Lower buy in amount, % based brokers has the advantage.
Break even in this case is around 14,666.67