A Chiang Rai tunnel collapse at a railway construction site on Saturday, June 20, left two workers dead and two others injured.
The incident occurred at around 6.45pm inside Doi Luang Tunnel in Chok Chai subdistrict, Doi Luang district, Chiang Rai. The tunnel is currently under construction as part of the Den Chai-Chiang Rai-Chiang Khong double-track railway project linking northern Thailand to the Thai-Lao border.
Two workers were injured in the collapse, while two others became trapped beneath debris after a section of the tunnel wall gave way.
The two trapped workers were later identified as 24 year old Thai national Apidate Kaewpraken and 29 year old Myanmar national Tu Tu Hun. Both were later pronounced dead at the scene.
The injured workers, 28 year old Thai woman Suppamas Khiaosawai and 28 year old Myanmar national Tun Tun Win, were transported to hospital for treatment. Channel 7 reported yesterday, June 21, that both injured workers remain under medical care.
Project engineers told Channel 7 that Doi Luang Tunnel stretches 3.4 kilometres. Tunnel boring work was completed last year, and crews are currently installing permanent concrete lining to reinforce the tunnel walls. Engineers said more than three-quarters of this work has already been completed.
According to project engineers, the collapse is believed to have been caused by an unexpected geological event. They said Chiang Rai has experienced unusually unstable weather and heavy rainfall over the past two to three years, resulting in significant water accumulation within rock layers beneath Doi Luang mountain.
Engineers believe the water pressure may have weakened temporary support structures, eventually causing the collapse. However, they stressed that the tunnel’s main structure remains stable.
Construction work inside the tunnel is suspended for two days while officials conduct a detailed safety investigation. Officials also said additional safety measures will be reviewed and strengthened to prevent similar incidents in future.
The Den Chai-Chiang Rai-Chiang Khong railway project has a budget exceeding 85 billion baht. The route spans 323.1 kilometres, extending from Den Chai district in Phrae province to Chiang Khong district in Chiang Rai near the Thai-Lao border.
Construction is expected to take seven years, with the railway scheduled for completion and operation in January 2028.
The project includes four major tunnels: Ngao Tunnel in Lampang, Song Tunnel in Phrae, Mae Ka Tunnel in Phayao and Doi Luang Tunnel in Chiang Rai.
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