First of all, you need to know how you want to learn. Training institutions? Still at school? At this time of self-study, you need a good teacher to lead you in and study actively in the right way.

What is your purpose in learning this language? Studying abroad? Or do you need to contact Southeast Asian countries to do business? If I am only interested in learning, I personally think any language will do. Southeast Asian languages are easier to learn than European and American languages. At present, Southeast Asian languages have great prospects. Anyway, as long as you learn well, you can have a meal everywhere. You can reply to me directly if you have any suggestions.