So how many developers do you actually hire out of Thailand? The prime minister of Thailand earns 3804 USD per year. If you seriously hire them at $380k, that's 100 times what the leader of their country earns. The US equivalent would be $40 million a year. Seemingly, every even remotely qualified person in the country would be rushing to apply. No need to immigrate and go through the Visa process? Earn enough money to buy your entire hometown within a few years?
Surely, there has to be some sufficiently motivated and intelligent person born in Thailand who is able to do the work you require. Have you hired any of them?