When using my Wise card, 2 cases :
1- If I already have bahts in what they call a "balance", I am debited in THB with no fees ar all
2- If I only have Euros in my balance in EUR, they convert the expense in Euro with a tiny conversion fee. The exchange rate is the real one, whereas Visa and Mastercard have their own exchange rates which are less favourable and my HSBC bank charges 2,90 % on top !
I use it to pay AirBnb in Thailand in THB (AirBnb fees are higher when paying in a different currency than the host). I cannot use my Bangkok Bank debit card, a credit card is required. Wise is not a credit card but it works
I generally don't use my Wise card to pay in bahts. I prefer to use my Bangkok Bank debit card and to make transfers from France to Thailand with Wise.
I leave Euros on my Wise "Balance" and get an automatic conversion from Euro to THB when the desired exchange rate is met in the market.