I've been waiting for the international schools to go public. Their quiet Thai approach has failed and now even the international schools have taken to public howling, and justifiably so.
Teaching always has been a special position in society, much like a physician or lawyer. It's not the same as being a hardhat or an IT wizzard. When one thinks of foreigners in the classrooms of your country's schools, the matter becomes more than special--it strikes sensitivities that are social, cultural, national in nature. Imagine an inflow of native speakers of Chinese and Japanese into the schools of your country. Wouldn't you want to know that everything's okay? So I'd say that, in primciple, some checks of credentials, character etc are reasonable.
However, this present nonsense in Thailand is tantamount to shooting one's self in the foot. (Most Thais shooting themselves in the head would cause less damage!)