It’s not a bad part of the world to be at all. I’m quite specialised in teaching IELTS so it’s good for me- the new middle classes want to get the hell out of Vietnam- even if it’s only for study. Fair play to them.
Cambodia can be disgraceful. I may have to go there soon on a visa run. My last one led to disaster and me ending up in the jungles of Myanmar (yet to be told, sorry. But I will.)
As a holiday destination, both countries are cheap, friendly people and plenty of fun to be had.