It's possible to get teaching work in most countries with a Certificate. Some countries also ask for a university degree; this is a requirement set by some governments. I'm not sure about the situation in Thailand. I have never worked there and I prefer not to give you incorrect or misleading information.
I suggest you contact the training centre you'll be studying with; they'll be able to tell you about term dates. They might also have contacts with schools in the country; some training centres help their students find work at the end of the course.
I'm am copying your question into the ESL jobs forum and the General discussion forum so that other people can respond to your post.