I’ve never taught English in Thailand, but I have known farangs (Westerners) who have. In Thailand, they are paid about the poorest of all the countries in the region. I believe farangs make more teaching in Vietnam and even Cambodia. A full-time salary for a Western native-speaking English teacher runs about 30,000 baht a month on average, often much less. At the current exchange rate of 34 1/2 baht to the US dollar, that works out to about US$870 a month. Of course, living expenses are lower in Thailand, and housing accommodation is often thrown in, but by no means always, nor is it necessarily desirable when it is. The low pay may not be an obstacle if you have a source of funds yourself and just want the experience.
Work permits can be red-tape hassle to obtain in Thailand, but the school that hires you will help take care of that. They cost almost $300 a year, which the school should pay itself. (It’s a sign that you’ve signed onto a bad school if they make you pay it.) Immigration and Labour have tightened up in recent years. Only foreigners with a bachelor’s degeree in a certain few fields, including education, are granted work permits, but any master’s degree or doctorate will qualify you for one. If you are over 60, you will be refused a new work permit, although extensions to the old one have no upper age limit. (Although retirement age being 60 here, there is no legal impediment to firing you for age.)
The low pay, especially compared with the extremely high English-teaching salaries and benefits in Taiwan and South Korea, and the red-tape hassles have driven away most qualified foreign English teachers. Many, perhaps most, farang English teachers here work illegally. That allows the school to pay at the bottom end of the scale, and you generally get no benefits. Farang English teachers have actually gained a bad reputation in Thailand in recent years, especially in Bangkok, because of the fly-by-night schools that recruit heavily for “teachers” from the backpacker areas like Khao San Road. The backpackers may or may not be native speakers, are almost never qualified and see it simply as an opportunity to extend their stay in Thailand for a few weeks. And my apologies to the backpackers on this board who may be reading this, but they also have a reputation for smelling really bad, a reputation that is not entirely undeserved.
There’s also a strict pay dichotomy. Americans are paid the highest, and so, too, the Brits I think. Maybe Canadians. For some reason, I believe Aussies and Kiwis are paid slightly less. Then comes a huge drop as Filipinos are paid much less, followed by Indians, and I believe Burmese English teachers are paid the lowest of all. A lot of the less-reputable schools will look for only Filipinos, Indians and Burmese, to avoid paying a decent salary.
Having said all of that, I’ll refer you to an excellent 50,000-word essay about teaching English in Bangkok othat appears on the Stickman website. Stickman is a Kiwi of my acquaintance, an extremely nice fellow who has worked as an English teacher in Bangkok, and his weekly columns on Thailand and what’s happening in Bangkok have a wide readership. The essay is here.