I used to do care work in Aus before coming to SEA, but haven't done any here. My gut feeling is that it would be difficult to find work in that area as a foreigner. As for the TEFL certificate, he could get a job here on that, I did for about a year and it wasn't that hard to find the job, but that was 3 years ago, don't know what it's like now. Be careful of the school though, talk to ex teachers and current teachers if possible and find out if there have been complaints about them from teachers or students.
Check out www.eslcafe.com
they have forums where you can talk to current teachers and they also have job classifieds.