It's not rocket science:
1) Pay better salaries for truly qualified candidates - pay peanuts and you get monkeys
2) Offer a streamlined visa/work permit process, assuming that the basic qualifications and teaching requirements are met
The solution to hire non-native speakers is an idealistic one.
To overcome prejudice will require years, if not decades.
However, all this requires coordination, critical thinking, reform and planning that Somchai is unfortunately, incapable of, so - never in a million years!