Shopee set up their system to lure you using shopee pay.
I plan to buy 1 item below cost RM15.44. Preferred seller and there is free shipping symbol on the product page for order above RM15.
I put in cart and ready to check out.

Later when I want to pay and tried to select free shipping voucher, shopee said current payment method does not meet voucher t&c.
Fine. I can't top up exactly RM15.44 as the price including shipping is RM20. Since I dont have enough balance I can't use shopee pay, therefore I can't use the free shipping voucher. So I top up RM 20.

When I top up and I can select shopee pay as payment method, now the free shipping voucher term has changed.
Now the say I can't use the shipping voucher because available logistic don't have shipping discount. Pretty shitty.
I purchased anyway because what else I can use with my shopee pay money?

Shopee free shipping used to be more flexible before and now they are really tightening the rules. Keeps you hooked on buying in shopee.
Their shopee pay system is designed intentionally to put your money in their account so that you will carry on with your purchase.
You can never know beforehand if you really can get free shipping. Even if you choose shopee pay, later then can say the product is not included in the T&C.
So buyer be aware.