You know, but the staff at Royal Thai Consulate does not know and now HCMC is being recommended by many as the place to go. So your friend is caught in that wave of people seeking a Non ED.
Fly back in on visa exempt and sign up at a real University. Sorry to be so blunt but what is in the mind of people ? A 19 year old sign up for a language course at an informal school. Surely that has raised the alarm bell. No need to put your comments in Capital letters.
the easiest way to to go to Savannakhet, upon your arrival and get the One Year Multiple Non O. This gives you the flexibility to go out and in, every 90 days.
they allow two land border entry. For a quick border run you will get the "day pass" to stay a few hours there. Easy. Stamp out of Thai, walk across, stamp into Myawaddy, nowadays they prefer THB500, after an hour or so back over the bridge . stamp back into Thailand, no question ask.