Two women were nabbed with a large haul of crystal methamphetamine and speed pills worth about 88 million baht on the Don Muang Tollway late on Wednesday night.
The arrested drug suspects were identified as Juthamas Kerdsang, 30, from Rayong, and Piyapha Nilkhuha, 24, from Bangkok.
The women were found with almost 300,000 methamphetamine pills and 10kg of crystal methamphetamine, widely known as ya ice, police said.
They were charged with possession of Type 1 narcotics with the intent to distribute, Pol Lt Gen Wanchai Thanadkij, chief of Provincial Police Region 6, said yesterday.
Police allegedly found the drugs in the suspects' car when they stopped to pay the toll fee.
Pol Lt Gen Wanchai said the drugs had been smuggled from the North to be stored in Pathum Thani. The suspects had picked up the drugs from some people at a hotel before heading back to Bangkok, he said.
Ms Juthamas allegedly told police a man called Hia hired her for 100,000 baht to take the drugs from the hotel and deliver them to a customer.
Hia was supposed to give her details later on the phone, but she was arrested before the man called, Pol Lt Gen Wanchai said. He said the case was linked to a drug trade network in Phitsanulok prison. The drugs came from a major dealer in the North.
Provincial Police Region 6 and the Office of the Narcotics Control Board have been pursuing the gang for some time. They would now expand the investigation to hunt for more members of the gang.