Originally Posted by ginocox
Any idea why they prefer overseas candidates?
Many prefer to hire candidates with current/updated western qualifications and/or fresh training/experience in whatever new trend is being pushed in the home country's curriculum. It makes a certain degree of sense, as after 7 years in BKK, I will admit to having lost some of the edge in regards to U.S. curriculum/ outcomes/ methods, etc. It's just harder to stay on top of things while in Thailand, unless you're at one of the handful of top schools in the country (that provide extensive professional development support/travel overseas for additional training, etc). My school does offer some of this, but it isn't a U.S. school, so my 'home curriculum' skills have certainly become somewhat outdated.
That said, as a former Head of Department at one of Bangkok's most academic (but smaller) international schools, I had less problems - in general - with local hires.
We, of course, required degrees in education (or subject specific degrees and 3+ years of teaching experience in a 'similar school setting'... i.e. primary/secondary school, not a language school) and a minimal level of experience.
As to the original query, we did have one German fellow teaching Math/Science. His English was quite good but language instruction was not his area. After about 2 years, he returned to Germany to finish his Ph.D. in the sciences (cannot recall the emphasis).
Anyway, I'm sure that if the OP hunts around a bit, he will find a teaching position. The online Cert.TEFL will probably not be viewed kindly, however. I would actually advise trying to sell the IT teaching abilities and not simply the English language angle. All of the better schools teach their computer classes in English. This could mean the difference between a mere 35,000 baht per month and 60,000+ per month.