What are the visa extension and re-entry options for someone in Buriram, Thailand?

You're right next to a border, at around an hour of distance. Lucky you.

might help

Let's get your terminology straightened out; I doubt you entered on a 30 day waiver because if you did you couldn't get ANY 30 day extension:O Visa waiver entries can't be extended

Let's go with the premise you entered on what's called a 30 day visa exempt entry stamp because that one you can extend for 30 days at the immigration office for 1900baht

After that stamp runs down, you go to the border, stamp out of thailand, stamp in&out of another country then stamp right back into thailand to get a NEW visa exempt entry. You can do TWO visa exempt entries in a calendar year (Jan 1 to Dec 31).

Doing it on or after Oct 1st will get you a 45 day stamp instead of a 30 day one and you can extend that also for 30 more days at the immigration office

The closest border to you in Buriram is the Chong Chom / Osmach border in Surin Province.