The fact that the consulates don't take MOE paperwork with beginner/intermediate on it is WELL KNOWN and has been going on for over a month now. I'd say their school doesn't know what they're doing.
The proof of funds is by showing a bank book, so have his parents who support him put money in his thai bank account to meet the proof of funds
I think it raised far more flags that a french person is applying for an ED visa to study ENGLISH in a private language school in thailand. I mean french people take english in school.
Still, if they can't wait it out in Vietnam to get the correct documents from the school AND to meet the proof of funds, they should take the advice
@Amor****
offered and fly back in on a 30 day visa exempt entry make a new plan and try again.