Update on Den Chai-Chiang Rai-Chiang Khong Double-Track Railway Progress at 59%, Advancing on Thailands Longest Tunnel

The State Railway of Thailand (SRT) updated on the northern double-track line from Den Chai to Chiang Rai and Chiang Khong, reporting an overall construction progress of 59.570%. They have adapted their plans to cope with the severe PM2.5 pollution crisis in the north, ensuring continuous work without interruption. All contracts are being expedited to meet the service launch target in 2028.

According to reports from the State Railway of Thailand (SRT) on the Den Chai–Chiang Rai–Chiang Khong double-track railway project, which covers a total distance of 323 kilometers and has a construction budget of 72.835 billion baht, as of March 2026, the overall accumulated construction progress stands at 59.570%, slightly ahead of the planned 59.448% by +0.122%. Currently, northern Thailand faces a severe PM2.5 pollution crisis exceeding safety standards. The SRT has adjusted its operational methods to align with this situation, maintaining continuous construction work with the goal to open services by 2028 as scheduled.

A detailed look into the three contracts shows contracts 2 and 3 exceeding their progress targets.

The project is divided into three construction contracts, with progress details for each as follows.

• Contract 1 (Den Chai–Ngao) Progress at 59.227%, behind schedule by 5.710% due to obstacles from flooding and complex terrain. The SRT is accelerating work to get back on track.
• Contract 2 (Ngao–Chiang Rai) Progress at 63.157%, ahead of schedule by 3.304%.
• Contract 3 (Chiang Rai–Chiang Khong) Progress at 55.064%, ahead of schedule by 3.700%, focusing on connecting the rail system to the border trade gateway.

Highlight: Drilling of the "Ngao Tunnel" preparing for breakthrough by late 2026.

The tunnel excavation, a core part of the project, has seen notable progress, with three out of four tunnels already broken through.

• The two tunnels in Phrae Province, totaling 1,059 meters, have reached 64.66% progress.
• The Ngao Tunnel in Lampang Province, the longest in Thailand at 6,211 meters, has progressed 79.37% with a planned breakthrough on 12 December 2026.
• The Mae Ka Tunnel in Phayao Province, 2,700 meters long, has reached 74.33% progress.
• The Doi Luang Tunnel in Chiang Rai Province, 3,400 meters long, has 70.25% progress.

All tunnels remain on schedule, with three already broken through. Only the Ngao Tunnel remains, with its breakthrough planned for 12 December 2026.

/ The Den Chai–Chiang Rai–Chiang Khong double-track railway construction project is a key strategy in developing the country's transportation infrastructure. Starting at Den Chai Station in Phrae Province, it traverses 59 subdistricts and 17 districts across four provinces: Phrae, Lampang, Phayao, and Chiang Rai. Upon completion, it will improve travel efficiency for passengers and freight, reducing travel time by approximately 1 to 1.5 hours compared to road travel.

Moreover, this route will play a vital role in linking the northern economy to the Thai-Lao border and the Greater Mekong Subregion, supporting cross-border trade and cargo transfer to Laem Chabang Port. It will also help reduce overall logistics costs nationwide. The line features beautiful natural scenery through mountains, bridges, and numerous tunnels, which will promote tourism and generate income for communities along the route. This aligns with the government's infrastructure development policy aimed at sustainably driving the national economy.

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