Border patrol police seized 40,950 methamphetamine pills abandoned on Highway 212 in Tha Uthen district late on Sunday night.
Pol Lt Col Thanapol Thaonu, deputy commander of the 23rd Border Patrol Police (BPP) Unit, said the meth pills were manufactured with with a new formula, as they were coated with crystallised methamphetamine.
The seizure was the first of this kind, he added.
Pol Lt Col said a BPP unit was on a regular patrol along Highway 212 when it found a bag containing 20 bundles of meth pills left by the road near Hat Sai Phe village in tambon Nong Thao.
It was believed the drugs had been smuggled across the Mekong river from neighbouring Laos.
An investigation was underway to find the origin of the drugs.