Border runs are currently history even if the boarders were open. If you crossed a border a Thai pass would need doing and PCR tests and everything else that goes with it. It would be the same as any visitor coming to Thailand.
Go to immigration taking a passport photo and proof of where you live with you. A letter of residence is 300b and you usually have to come back to collect in 1 hour.
there was a blanket ban on them all during some of the covid restricted times. If some hotels have restrictions on now I can't answer why they have. Maybe there choice if hotel is quiet as they need maintenance to keep clean.