Wise lets you convert USD to THB in same wise account, so you can do it when rates are favorable, then hold or send the THB to your Thai account. You can convert back to USD when rates go the other way…giving you the option to benefit from good FX rates.
yes, they are probably after expats with tech skills that are being paid relatively well and working for well established companies - given these are multi year visa, they want to ensure stability in work and income for these candidates.
For the ‘Work From Thailand’ visa, there is not a requirement to work for a public company, just that audited financials for the last three years show a total revenue to be at least $150 million USD - yes still quite a high bar.