TESL diploma/ CELTA ?

I am a non-native English speaker and I really want to teach abroad (Hopefully in Japan, Korea, Vietnam) but unfortunately, I've come to a realization that being a native speaker is a must to teach there. I am currently doing my diploma in TESL.
I am wondering if I could teach abroad with only my diploma? Should I also take up CELTA for safety measures?
Your replies are very much appreciated. Thank you