The accident happened at 1 am on the downhill Mittraparb Road in Muaklek district in front of the Phetcharat Boy Scout Camp.
Police said the part of the road was steep and it was slippery following rains, causing the bus to lose control and turn over.
Phrakru Photichayanurak, 58, monastic chief of Sakon Nakhon’s Wanornniwas district was crushed and killed by the bus.