A traffic policeman was found drowned in a shallow ditch in the middle of a road in Udon Thani's Muang district.
Muang Udon Thani police said Sen Sgt Maj Suwan Wongwairat, 47, and his motorcycle were spotted lying in the middle of the Khon Kaen-Sakon Nakhon bypass.
Udon Thani police chief Maj Gen Woranat Phanphon said Suwan was heading home after his shift.
Woranat said Suwan might have been ill and fallen into the ditch.
He was found with his head in the water and rescuers said he died about 20 minutes before they arrived. Rescuers unsuccessfully performed CPR.