Do I need to speak the local language to teach English?
Not necessarily. While it would always help if you know the language of your students, this won’t always happen. Particularly not if you teach classes where there are five or six different mother tongues in one classroom!
Actually, modern English teaching requires students to use English as much as possible in a communicative way, and we should, as English teachers, try to limit the use of any other language in the classroom.
If you move to a new country though, you’ll still probably want to learn the local language. This has so many benefits, including giving you greater insight into language learning, helping you understand language concepts and see differences (e.g. tonal languages, where the use of tone alters meaning) between different languages. You’ll also have the quite obvious benefit of being able to communicate in the local language as well!