A 35-year-old Ayutthaya man has been arrested after dozens of sacks containing 8 million speed pills were found hidden in his van parked at a shopping mall in Muang district of Chiang Rai province.

A combined team of soldiers, narcotics suppression officers and local police, led by the Pha Muang Task Force, made the arrest after tracking a white Honda Spada van with Khon Kaen licence plates, members of the arrest team said on Saturday.

Authorities said investigators received intelligence reports on Friday afternoon about a large shipment of drugs being smuggled from the Chiang Rai border via Muang district for distribution to other provinces in Thailand.

Officers subsequently tracked the van along Phahon Yothin Road before it returned to tambon Ban Du in Muang district of the northern province. The vehicle was later parked at a shopping mall.

The arresting team then moved in to inspect the vehicle and found a man behind the wheel. A search found numerous black plastic bags inside the vehicle.

The bags contained 39 large sacks, each filled with speed pills, totalling about 8 million. The suspect, identified as Peerakorn (surname withheld), a native of Bang Pa-in district of Ayutthaya, was taken into custody and handed over to local police.

Authorities are expanding the investigation to seek others involved in the drug smuggling.