Answer:
I can only comment on teaching English as a second language in South Korea, since it is the only country in which I can speak from experience. You can find teaching jobs with a Bachelor's degree in any field of study. While it is encouraged for you to have a CELTA or a TEFL certificate, it is not essential. Having one will get you a better salary in some cases. It's a good idea to talk to someone who has been there before and can recommend good places. In my case, I didn't talk to anyone and I ended up being very lucky anyway by landing a good job in a good school with a good director. Not everyone is fortunate like that and there are some people who have had bad experiences. I would like to recommend Canada-ESL.com as a go-to point to find out more about the process. If you're serious about going, leave a message and hook yourself up with the latest top jobs. Check it out at http://canada-esl.com/teachkorea.html . Hope this helps!