Thailand has a smaller GDP than the countries where native-English speaking teachers come from. Those teachers can't expect big money, but they should expect the salaries to rise with inflation. Many salaries here have been 35,000 for 15 years! There are no excuses for that. Well, other than sheer greed.
It's like my Thai friend in Korat who has an agency says, "We can't pay more because the rules are the rules". Like they're not so much his rules but a strict set of moral principles that he won't stray from and people should respect. And as I always say to him when he desperately asks for advice outside of paying more money, "foreign teachers are not obliged to come and work for you. But you are obliged to provide native-English speakers (white people) to the schools who employ you. It's advertised in <i>your</i> brochure <i>and</i> theirs.
My friend in Korat has had it far too good for far too long. In the last maybe three years, his business has gone to the dogs. He can't find new teachers and the ones he has are basically children themselves - looking to take selfies with the kids and post their fake benevolence online. And this is where Thailand TEFL is heading. That's why I teach Chinese people online. I can't help my friend because he's only thinking money. He won't take a satang less.