Wanchai Saengkhao, the 22-year-old hired by the SRT to make beds in sleeper carriages, said he got away with earlier rapes because his victims were too scared to report him to police. That encouraged him to make a third attack, this time on a 13-year-old girl identified only as Nong Kaem, according to investigators.
His attack on the girl has generated demands on online social networks for the death penalty in rape cases.
Police took the suspect to the crime scene for a re-enactment early Wednesday to avoid a repeat of the angry scenes of a day earlier at the police station in Prachuap Khiri Khan, where the rape occurred on a train bound to Bangkok early Sunday.
Police led by Pol Maj Gen Thanate Sunthornsuk escorted Mr Wanchai to Wangpong train station where the same train Nong Kaem travelled on was stopped.
He told police he had taken methamphetamine, or ya ba, after the sleeper train left Nakhon Si Thammarat station, and drank beer with other employees in the fourth sleeper car.
His young victim was sleeping in the third sleeper car when he allegedly attacked her.
Mr Wanchai pointed to the spot where he sat, showed how he switched off the light in the car, and got into the bunk bed where the girl slept. He strangled her and hit her in the stomach, he told police, until she passed out, then he opened the door to cover the noise and raped her.
Afterward, he searched her bag and took her iPhone and iPad. When the girl regained consciousness he covered her mouth and strangled her again, and raped her again, he confessed to police.
He later pushed the girl's body out of the train window and then threw out her clothes and the blood-stained bed sheet. The suspect took her bag and sat in the train until it arrived in Bangkok. Mr Wanchai said he sold the smartphone, which police later tracked to arrest him.
Mr Wanchai said he remembered that the girl was still alive when he tossed her from the train. However, his statement contradicted an initial post-mortem examination which concluded she was killed on the train.