Moving to Thailand (Bangkok)

I hope somebody can guide me here. I am planning to move to Thailand in the very near future. Been there 3 times,I just love the people and the Country..
Planning to come there and obtain a TEFL Certificate to teach English. The question is I am non native English Speaker. But I have passed Cambridge 'O' Level certificate in English, and I believe my English is pretty good, writing and speaking.
Would there be a problem in getting a job?.
And what is the best visa that I should apply to get entry into Thailand. I hold a Canadian and UK Passports..
Many Thanks.
( Also coming over to Pattaya and Bangkok early Dec. for a quick holiday before I move there for good early next year.) Perhaps I can attend I/Nations in Dec.