@Peter *******
heed the advice you've been given. There is no need for them to slog all the way to the Kanchanaburi border with Burma to get 30 more days,.
As
@K**
said they can go to the immigration office and get a 30 day extension on their 30 day visa exempt entry for 1900baht.
After that, if they need more time they can go bounce out and back by land for a new 30 day visa exempt entry.