Fitting into Korean society can be tough even when you know the language well enough.
I just got bored of teaching English, so I learned enough of the language to move into something else.
I have a few friends making a career of it. They usually get a master's degree and go teach esl at a university or get a teaching certificate (there are a few American ones you can get abroad) and teach at private international schools. A few others just start their own business. You can actually do quite well if your reputation is good, as Koreans don't hesitate to spend money on quality education.
oh those university jobs are incredible, great wages, a lot of respect, and it feels like a proper job with benefits and retirement programs and what not. Thailand isn't looking to hire those people though, they are looking to employ teachers at state schools, mostly elementary schools i would imagine and the classrooms will probably be packed to the gills!