Okay, so in this scenario, either 1) the developer is losing money on every sale to a Thai customer, or 2) the developer is overcharging US customers. Either way, the developer does indeed seem to lack any incentive to have separate pricing for Thai customers; why take on those support costs for a fraction of the revenue when you still have Americans paying full price?

The demographics that can't afford the game (e.g. certain overseas countries, or low-income individuals even in domestic markets and otherwise-more-affluent overseas markets) will be out of luck only until the game goes on sale (whether temporarily or permanently; older games tend to be cheaper than newer games).

In other words: setting a lower pricepoint for specific countries to attract more sales in those countries is a pretty major footgun when it comes to actual revenue from those sales. Better to keep the price even across all markets, then only drop the price if you want more sales (and in smaller increments than "here's a 90% discount just because you happen to be in Thailand"). Trying to establish different prices for different locales is a premature "optimization" at its worst.

The actual reason for separated national markets was that selling to a national market once upon a time involved actually getting a physical good (e.g. a cartridge or optical disc) to a customer in a different nation; for most game developers, it's easier to go through a distributor for that particular market than to try to tackle all the logistics themselves. Nowadays there's no physical good being exchanged, so there's really no point to dealing with that kind of market segregation.