Most programs only require a criminal background check and a bachelor's degree. If you enter with a program, they usually do the TESOL training, IF it's required. (This is so with Korea, though you'll have to check other program-specific requirements, depending on where you want to teach. I.e. teaching in Europe and the Middle East? I've heard different qualifications are necessary (like, be a real teacher). But the trade-off (again, so I've heard) is more money. Just depends where you want to go and what you're willing to do. For most places in Asia, you shouldn't need TEFL certification. But things may be changing.