I can only tell you what I've heard - but have not seen this with my own eyes:
According to an announcement that was published back in March, travelers entering Buriram via car, bus, rail or air, will be flagged upon arrival and either placed in a 14 day quarantine (if they are arriving from abroad) or a 14 day isolation for inter-province travelers. As far as the efficiency of these checks at the bus or rail stations, I really have no idea. I do know that they stop all cars entering the province. My partner Jai has family members residing in both Surin and neighboring Ubon Ratchathani who have not visited their homes here in Buriram since this mandate was announced.
My guess is that some travelers make it in - and some don't. Right now a farang and his Thai wife who live near Jai's home were placed on 14 day isolation for making a one day shopping trip to Ubon and then reentering Buriram by car.
All said, I would imagine this interprovincial travel restriction will be lifted (or modified) soon. Fingers crossed.