Pol Maj Gen Puthichart Ekachant, deputy commander of the Narcotics Suppression Bureau, said on Saturday that police arrested the four men, aged between 37 and 49 years old, at a traffic checkpoint in Chumphon's Tha Sae district. The suspects were driving two pickup trucks and a sedan.
Pol Maj Gen Puthichart said the speed pills were hidden in gas tanks under the vehicles.
The suspects told police they were paid 50,000 baht by an inmate at a prison in a southern province to transport the drugs to his agent in Surat Thani.
In Songkhla, police arrested two drug suspects and seized 20,000 speed pills at a gas station. Investigators later found out that the drugs were brought from the same group of people who were apprehended in Chumphon.