Ragamuffin,
I don't know about your qualifications - I am a qualified UK teacher and teach Maths. All posts are interviewed for, I suppose this certificate will get you an interview. There is a job opening up today- - A part time ESL teacher for our "Junior Academy". It is only 6 hours a week, and does not come with work permit. Full time jobs do appear quite frequently - and the best time to look is the mid to end of Jan, for jobs starting in August. The first day back in Jan is when we have to say if we are staying for the coming academic year. Full time jobs come with work permit along with good salary and some extra benefits, depending on the package being offered.
Anyway, keep an eye on
www.phuketgazette.com ,
www.dulwich.ac.th and
www.tesjobs.co.uk for upcoming positions.
Hope this helps.