Acting on tips-off, they found a fertiliser bag containing the drugs by a utility pole on Mukdahan-Don Tan Road near a petrol station in Ban Pho Sai village.
They kept the location under surveillance from 5 to 7am, but no one came to collect the bag.
Pol Lt Col Thirdrit Suwanprathang, commander of the Border Patrol Police Company 234, surmised that a drug ring left the bag there to be picked up by a courier.