I use the i-to-i forums as well and while I don't doubt that you were told on there that you could work in Vietnam without a degree, I suspect it wasn't actually i-to-i who said it. For some reason that forum is frequented by people who insist that you can work in Vietnam without a degree and they know that because they are doing it. They may well be doing it but I assure you that they are not working legally.
Unfortunately the requirement for a degree is simply to satisfy Governments that you have a certain standard of education (16+ years in full-time education I think). While most countries will accept a degree in anything, there are some that will insist on candidates having a relevant degree.
If you are really keen to teach, you will find a way to make it happen, albeit not necessarily in the country you had originally intended. That's no bad thing though. I originally had my heart set on Spain, and yet ended up first in Vietnam, then in Portugal and now in Poland. I guess what I'm trying to say is that just because something wasn't your first choice doesn't mean it's not a good choice or that you won't enjoy it.