It's not just the cost to send.. You need to look at Total cost, ie Funds+fees in relation to currency received. It's probably a lower fee, but the exchange rate is lower.. Resulting in a higher overall cost per baht received.
Basically.. They charge a lower fee, but screw you on the rate!
Also my bank doesn't charge me to receive the transfer from wise, it does for others I've tried...
as Brandon says... But I'll add.. Before commencing.. Get a 'Bill of Quantities' this details everything thats included in build and itemises the costs of each item.. For example the cost if each sqm of tiling.. Materials and labour.
The more details in this agreement, the less confrontation you will have.. A good reputable builder with have no problem with it.. The others hate it and will discourage it.. Because they know they can add.. And add.. And add.. As it goes along'
And... Take charge, don't let them deal with your wife.. Keep her out of it! The builders know that ladies won't want to have confrontation with 'senior professional male' and use this to their obvious advantage to push things through..