Sara for wire transfers in USD the Thai bank sets the rate. Thai bank rates are decent for USD, certainly better than you'll get for THB from a US bank.
For card withdrawals, it's the Visa rate. This is also a good rate, maybe 0.5% on average markup. It's set by Visa, Schwab don't charge anything.
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Both methods (and Wise too for that matter) work out about the same in terms of cost, they are all inexpensive. It depends whether you need a large sum of money in a bank account, or a smaller amount of cash, as to which you use.