only cover during flight if im not mistaken. Any accident after you leave airport/before you arrive they dont cover.

I plan to use this WMC for any payment incurred in Singapore .

I noted that RM1 = 5 Ampoints
5,000 Ampoints = 1,000 Miles
RM 1 = 1 Miles for overseas spending.
RM 3 = 3 miles

I also aware that there are some bank/ MasterCard/ charges for overseas spend

I have several cards in Singapore
I group the cards as below:

Pay with Paywave : SGD 1 = 4 Miles
Dining expenses : SGD 1 = 4 Miles
Overseas spend (outside Singapore) : SGD 1 = 2 / 2.4 Miles
Local general spend : SGD 1 = 1.2 / 1.4 miles

So I will continue to use Singapore cards for the following as above except the local general spend, overseas spend (spend in Malaysia). I will use ambank WMC instead.

Above is my strategy to accumulate the miles . Please advise

Yes. Both PPV and PPA awards 4 miles per dollar (SGD 5 as per block)