with the correct paperwork from School or University they surely will help you get the extension into your passport. However without supporting paperwork they will give you only a 7 day denial stamp, means the extension is VOID.
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.