Non-international undergraduate degree

My girlfriend would like to study english, at first she was thinking to study at a language school or something similar.

Then i had the idea that we could study this together at a university (English is not my mother tongue), because this would give us a degree.

Until yet i don't have a degree, i also don't need one, but who knows what happens in the future and when i might need one (maybe to get permanent residency or something similar)

I think this would be easy to get if my girlfriend studies it anyway, and it looks like this is high school level english, so i don't see a problem in passing the exams after i learn some theory like grammar rules.

I expect that the exact requirements depend on the university, but maybe somebody can tell me how this is usually handled:

Are the non-international study programs open for foreigners?

Do they require a Thai language exam? (For something like "business studies" in Thai i would expect it, but i assume that "English" should be possible without an exam regarding Thai language skills)

Is there an age limit?

I know that Thais, before they attend a university, have to make an exam which gives them some score. Would i have to do this?

Is this exam related to the degree program for which you sign up or is this a general exam? Is it necessary for any university or just the government universities?