A worker manning a machine to drill a cable tunnel in Nonthaburi fainted when he went underground to check out why his machine was malfunctioning.
The man was working on a project laying cables for the Electricity Generating Authority of Thailand (Egat).
Officers from the Sai Noi Police Station said the incident took place at 4am on Monday inside a 3.7-metre wide, 7m long and 4m deep manhole.
It took rescuers almost an hour to carry out the worker, who was only identified as Thongchai, 35. He was rushed to the Sai Noi Hospital. Before crawling into the tunnel, the rescuers pumped it in with oxygen to ensure their safety.
Thirapat Panya, the engineer in charge of the operation, said Thongchai was operating the rig until it stopped at a depth of some 360 metres from the manhole. So, he said, Thongchai offered to go down the manhole to check, and Thirapat and another engineer Witthaya Phowiset joined him.
Thirapat said they had walked down the tunnel for about 200 metres when Thongchai said he was tired and asked to rest. However, he soon fainted.
Thirapat then alerted workers outside to organise a rescue mission.