Police say they confiscated more than 1,000 kilogrammes of crystal methamphetamine and more than 5 million speed pills in a series of drug busts in recent days.
The huge haul of crystal methamphetamine, known as "ice" was found after two trucks were intercepted by police in Phichit province on Sunday as they were heading South towards the central region.
"The drugs were to be sold in Bangkok and neighbouring provinces," Narcotics Suppression Bureau chief Pol Lt Gen Chinnaphat Sarasin said.
He said that Kriangkrai Phetchan- tharangsi, 22, and Worachun Sae-Wang, 21, admitted picking up the drugs from a major drug figure, based in the North.
The drugs were hidden in the rear of one of the trucks, according to investigators.
Another suspect, a Myanmar national, was also arrested for working as a navigator in the other truck.
The seizure of the large haul of ice in Phichit came one day before the Loy Krathong festival on Monday.
"Many drug gangs often transport narcotics during festivals," Pol Lt Gen Chinnaphat said.
Police also seized 8kg of ice at Don Mueang airport following a tip-off the drugs were to be smuggled into Japan. The drugs were hidden inside a wall clock, police said.
Elsewhere, police arrested Chakkaphong Huatlim, 42, along with four accomplices, for possession of 2kg of ice, 40,000 speed pills and a kilogramme of marijuana in Prachuap Khiri Khan's Muang district.
Investigators said the gang usually ordered drugs via social media and received them from couriers in Laos.
The latest bust took place in Nakhon Phanom when five smugglers were arrested and more than 5 million methamphetamine pills found in two cars in Sri Songkhram district on Tuesday night.
Acting on a tip-off, a team of police, soldiers and other security officials was assigned to watch out for a shipment of drugs being smuggled into Thailand from Laos. They spotted two cars travelling from the border area in Ban Phaeng district late on Tuesday night.
They gave chase and stopped the two vehicles for a search in tambon Hat Phaeng of Sri Songkhram district.
A total of 25 fertiliser sacks were found inside the cars. They contained more than 5 million speed pills, officials said.