I’ve been teaching ESL courses in Japan for more than 20 years, but I don’t have an MA. That said, these days your chances of getting a decent job in the field are considerably enhanced by the acquisition of an advanced degree. I googled “TESOL degrees” and copied the first several URLs into the source box below. TESOL degrees can be earned on-line, but be careful – most reputable programs require practicums (you are observed by trained teachers while you conduct real classes in real classrooms) and many also require minimal stays during the summer. Good luck!