When I asked to my Thai broker about taxes on crypto profits, I was told that things are still unclear regarding this issue and that, at least for the time being, they were not reporting anything to the authorities regarding crypto transactions.
As for the bank, it doesn't care about money coming into your account, at least as long as it's not a very large amount.
So one could say that if you keep a low profile, no more than a few hundred thousand bahts at a time, you should be able to cash in tax free.