Two Xmas's ago, the hotel fucked up my booking because of the midnight/change date scenario. The night porter didn't know to expect me and wouldn't/couldn't give me a room.
All the usual places with 24 hour reception were full, it being high season, but I got a room for the night at a short time hotel next to Tims in Second Rd. Less than basic, but clean, 400 baht, and no questions asked when I took two different birds there over the next couple of hours.