The only thing that comes to my mind is that there is some kind of exception for crypto payments coming from abroad to the account of certain companies. Otherwise, I don't see how anyone would ignore the very strict laws in that country, although until recently I thought that the ban on payments with cryptocurrencies in Turkey was a serious matter, until a forum member explained to me that the law exists only on paper.
Soneva, the company that owns those resorts is based in Maldive, they are the ones taking the payment, and Thailand authorities have no say in what and how is paid, in the accounting it will still be the equivalent in thai baht, ฿ not
BTC lol, the customer can choose to pay in euros dollars or whatever the main branch of the company accepts.
So if I would own a house in Thailand I could lend it to you for 0.x bitcoin and my only trouble with the Thai authorities is to pay the taxes on the amount I made from lending you that, and of course, the contract between us will state the value in our national currency, not bitcoin.