
Initial police investigation into the ill-fated train suggested that switching error may have caused the train to derail.
The train heading to Bangkok from Trang derailed just about 100 meters near Khao Tao station in Hua Hin district of Prachuab Khiri Khan early Monday.
The incident killed at least ten passengers including a two-year-old girl. The train left Trang at 5.20pm Sunday and was scheduled to arrive Bangkok at 8.25am Monday.
"Preliminary police investigation suggested that switching error might have caused the train to derail as it was approaching the station," the TNA reported.
Rescue operation is underway to search for passengers trapped inside the train.
Police said earlier that most of the victims were killed from the impact of the derailment.
All southern route trains were temporarily suspended for one day following the incident.
State Railway of Thailand (SRT) president Yuthana Thapcharoen said it would take at least one day to clear the scene to allow the train services to resume.
The SRT president said a special committee has been set up to probe the cause of train derailment. Result is expected within five days.
"But I believe that it would take more than one day," he said.
Rescue trains from Bangsue and Thungsong stations of Bangkok and Thungsong station of Nakhon Si Thammarat province to help lift the derailed trains.