Rescue teams are battling to save two trapped workers as the body of their colleague was recovered from a collapsed train tunnel in Thailand.

Ekkarat Sriarayanpong, head of the State Railway of Thailand governor's office, said the corpse of one of three men buried alive in the railway project was found at 11am today, August 29.

Nakhon Ratchasima governor Chaiwat Chuenkosum said the body reportedly belonged to a Burmese national found near a truck under debris. He added that the vital signs of two other trapped workers were still being detected in scans five days following the collapse.

He said: 'Soil is the main obstacle to the rescue mission. We hope that the vehicles trapped in the collapsed tunnel provide a space that protects the three men. Workers in such places receive training in how to survive in the event of a collapse.'

More sniffer dogs were deployed while a Chinese engineering team shored up the supports of the tunnel. Sensors were also placed in different points along the passage to monitor subsidence.

Authorities were earlier installing a 10x10ft metal tube through the underground railway hoping to reach the survivors. They added support frames and mortar to keep the tunnel from caving in further.

A four-foot-diametre 'rescue tube' had been used to supply oxygen and emergency aid to the trio.

The three individuals were named as Chinese foreman, Hu Xiang Min, a Chinese backhoe operator, Dong Xin Lin, and a Myanmar truck driver.

The tunnel, set to link Thailand to China, reportedly caved in and trapped them despite no rain falling on August 24 evening.

The high-speed railway is envisioned to connect Bangkok to Kunming, China. The project was expected to be completed in 2028.