What are the best qualifications for highest pay


I am a certified teacher, and currently serving as an English language facilitator in the peace corps. I work, primarily as an ESL teacher, but also teaching teachers how to teach in a remote island in Tonga.

My question is I did not finish my masters in Education (specifically, general ed, but also ESL). I am a few classes short. Could I finish my masters while working in the Middle East (online)? Should I get a TEFL cert too? Which is more important to make the most money, or both?

Meaning I want to be in the top income bracket (5,000 USD per month), but I want to know what I would need to do that. I am currently a certified teacher with 4 years experience in both domestic and international. Would it be better to get my TEFL or finish my masters? Or both
Please help! Making life decisions right now :)