Seventy-four candidates were arrested for having radio-controlled receivers and batteries stuffed in their underpants while they took the exam.
Colonel Vinai Maneewong, the chief investigator, said each cheating candidate had to scratch his groin as if he had an itch, but would really be alerting Private Samrong Pongsakorn, the remote controller, to get the correct answers to the multiple-choice questions.
Samrong transmitted the answers in code from a room about 50 metres from the exam building. The cheats had each paid 40,000-50,000 baht (Pounds 1,000-1, 300) for the service.
Police have made 74 arrests, but believe that several hundred of the 10, 000 who sat the exam at the Ramkhamhaeng University campus were involved. The exam would have to be passed by a private, for example, who sought promotion to sergeant.