About TESOL

Some institutes don't require teaching experience, but most do. Even if you haven't even completed your undergrad degree, you can still be accepted into the program. You just have to pass a pre-test and interview.

Something that's definitely necessary is for the TESOL student to already have good English. A level high enough for him not to need any help with basic and intermediate grammar, spelling, pronunciation, and the like. The TESOL doesn't really improve one's English. It may do so marginally but what it really does is to teach how English should be taught.

By the way, TESOL is offered in many Asian countries, including Taiwan. Just make sure the institute is established and the instructors are qualified (have a CELTA/DELTA/TESOL/TEFL, native speaker/speaking) to handle the course.