Police Gen. Wichean Potephosree told the Bangkok Post 4,655 communities were searched in the operation, which ran from Dec. 21 through Wednesday.
Police confiscated more than 1.6 million amphetamine pills, 650 pounds of marijuana, 19 pounds of crystal methamphetamine, and heroin.
Wichean said five suspected major dealers were arrested, including police Senior Sgt. Maj. Pairote, who was fired from his Bangkok post in October.
He was arrested in Phetchaburi with 120,000 speed pills in a hidden compartment of his car.
Two other suspects were women of Burmese origin, Patcharee Lertluangchai and Orn Saengwong, who were arrested with 300,000 amphetamine pills in Pathum Thani.
Wichean said most of the drugs were smuggled across the border into northern Thailand before being distributed around the country.