
The 300-strong Big Cleaning Days force, with medical backup and sniffer dogs, will carry out urine tests in Klong Prem, Bangkwang, Khlong Pai and Khao Bin prisons and the Central Correctional Institution for Drug Addicts.
They will also look for mobile phones used to order narcotics.
Natthee said he had instructed prisons nationwide to conduct similar searches at the same time.