Soldiers arrested Sunantha Sangketkan, 31, of Tha Maka district, and Omkhwan Joonphan, 24, of Muang Kanchanaburi, in their red Toyota at the Thong Pha Phum intersection in Tha Khanoon subdistrict on Saturday.
The arrest followed a report from staff of the Thong Pha Phum prison that two women had managed to sneak methamphetamine pills to some inmates during a visit.
Officers said the women confessed that they had been hired to buy methamphetamine pills and deliver them to specified inmates. The pills were inserted into two straws hidden in their long sleeves while they were visiting the inmates. They managed to pass the straws to the inmates through bars while they thought the warders were not looking.
Miss Sunantha said she pretended to be the wife of inmate Chaloempol Nithiwong, 25, and Miss Omkhwan acted as the wife of inmate Suchart Phrammanee, 24. The men are serving jail sentences for trafficking methamphetamines.
Miss Sunantha said she had received a money transfer of 2,000 baht for the task and another 27,000 baht later for speed pills on Friday. They left the prison after Miss Omkhwan had slipped the two straws to Mr Suchart. A total of 188 speed pills were stuffed into the straws.
Both women had been released seven months ago from the Kanchanaburi prison where they had been serving time for trafficking methamphetamine pills. Miss Omkhwan is four months pregnant.
Authorities said the money given to Miss Sunantha had been transferred from a bank account of Rojarin Hadee, whose husband Pairat Thasri is doing time in Thong Pha Phum for trafficking speed pills. Mr Pairat confessed that he and the other inmates had ordered the pills, officials said.