The Den Chai–Chiang Rai–Chiang Khong railway line is a project of the State Railway of Thailand (SRT) and one of two extensions of the Northern Railway Line. Its objective is to support travel and freight in the northern region, including supporting the Chiang Khong freight transfer center currently under construction. This project will connect the North–South Economic Corridor from Thailand to Laos, China, Vietnam, and other economic zones under government policy. Construction was originally scheduled for 2017, but was postponed to 2021. In July 2018, the Cabinet approved the Den Chai–Chiang Rai–Chiang Khong double-track railway project, covering a distance of 323 km, with a total budget of 85.345 billion baht and a project duration of seven years.  The Ministry of Transport urged the SRT to begin land acquisition and bidding by 2021, with a five-year construction period and opening service in 2028.

History The construction project for the double-track railway line Chum Thong Den Chai - Chiang Rai - Chiang Khong, a distance of 326 kilometers, was previously studied by the Thai government in 1960 and surveyed the area in 1969, designating the route Den Chai - Phrae - Song - Chiang Muan - Dok Kham Tai - Phayao - Pa Daet - Chiang Rai, a total distance of 273 kilometers.

Later, in 1994–1995, the State Railway of Thailand (SRT) hired consultants to review the study results. The conclusion was that the Den Chai Junction – Phrae – Song – Ngao (Lampang) – Phayao – Chiang Rai route would shorten the distance to approximately 246 kilometers. Consequently, in 1996–1998, the SRT spent approximately 2.2 million baht on the project. The SRT then hired a private company to survey, design, and study the impacts, leading to a Royal Decree on land expropriation in 2001. In 2004, the then-government ordered another feasibility study, citing the need to connect with southern China. In 2008, a study was also conducted to connect the border of Chiang Rai Province and China's rail system.

Until 2010–2011, studies began on double-track railways to increase the width to 1.435 meters. In the case of the route in Chiang Rai Province, the route was separated to the second Chiang Saen Mekong River Port in Ban Saeo Subdistrict, Chiang Saen District, and the Thai-Lao Mekong River Bridge in Chiang Khong District.

The latest route studied has a total distance of approximately 323.1 kilometers, with a total of 26 stations passing through Phrae, Lampang, Phayao, and Chiang Rai provinces, and a tunnel will be drilled into the mountain to connect the route to Chiang Khong District.

In 2018, the Cabinet approved the construction project of the Den Chai-Chiang Rai-Chiang Khong double-track railway line, consisting of 26 stations, 4 cargo handling yards, 1 container storage yard, 4 railway tunnels, 40 roads over the railway, and 102 roads under the railway. The project began in Phrae, Lampang, Phayao, Chiang Rai, and Chiang Khong provinces.

On March 19, 2021, the State Railway of Thailand began opening bid envelopes via the electronic procurement system (e-bidding) from March 19 to May 17, 2021, and submitted proposals on May 18, 2021. The construction is divided into three contracts: Contract 1, Den Chai- Ngao section, 103 km long; Contract 2, Ngao-Chiang Rai section, 132 km long; and Contract 3, Chiang Rai-Chiang Khong section, 87 km long. The construction schedule is 5 years, with service opening in 2028.

On June 27, 2021, the Royal Gazette website published the land expropriation demarcations in some areas of Den Chai, Sung Men, Mueang Phrae, Nong Muang Khai, and Song Districts in Phrae Province ; Ngao District in Lampang Province ; Mueang Phayao, Dok Khamtai, and Phu Kam Yao Districts in Phayao Province; and Pa Daet, Thoeng, Mueang Chiang Rai, Wiang Chai, Wiang Chiang Rung, Doi Luang, and Chiang Khong Districts in Chiang Rai Province   to construct the Den Chai–Chiang Rai–Chiang Khong Railway Project 2021. This Royal Decree will take effect the day after its publication in the Royal Gazette (May 28, 2021). The land expropriation covers over 10,000 rai and 7,000 plots of land.https://www.thansettakij.com/property/481796

On December 16, 2021, Mr. Nirut Maneephan, Governor of the State Railway of Thailand, approved the construction contract for the Den Chai–Chiang Rai–Chiang Khong double-track railway project, valued at 72.92 billion baht, from three contractors: Contract 1, the Den Chai–Ngao section, is being awarded by Italian-Thai Development Public Company Limited (ITD) in collaboration with Nawarat Patanakarn Public Company Limited; Contract 2, the Ngao–Chiang Rai section, is being awarded by the CKST Joint Venture, comprising CH. Karnchang Public Company Limited, Sino-Thai Engineering and Construction Public Company Limited, and Buriram Panasit Co., Ltd.; and Contract 3, the Chiang Rai–Chiang Khong section, is being awarded by the CKST Joint Venture, comprising CH. Karnchang Public Company Limited, Sino-Thai Engineering and Construction Public Company Limited, and Chiang Mai Construction Co., Ltd.https://www.prachachat.net/property/news-828153

On December 29, 2021, at the State Railway of Thailand, Mr. Nirut Maneephan, Governor of the State Railway of Thailand, signed a contract for the construction of the Den Chai-Chiang Rai-Chiang Khong double-track railway project, as well as signing an Integrity Pact for cooperation in preventing corruption in government procurement between the State Railway of Thailand, which is the owner of the project https://www.facebook.com/pr.railway/posts/5344998998848261

When the project is completed, it will support travel, border trade, tourism, and logistics in the upper northern region, including supporting the Chiang Khong goods transfer center, connecting trade along the North-South Economic Corridor from Thailand to Laos, Burma, and southern China. It will also help accelerate the development of the Chiang Rai Special Economic Zone, which the government is pushing for.http://www.prachachat.net/property/news-283935

Districts through which the route passes DistrictProvinceChiang Saen / Doi Luang / Wiang Chiang Rung / Chiang Khong / Wiang Chai / Chiang Rai / Pa Daet / ThoengChiang RaiPhu Kamyao / Phayao / Dok Kham TaiPhayaoNgaoLampangSong / Nong Muang Khai / Phrae / Sung Men / Den ChaiPhrae

Construction contract ContractPeriodDistance (kilometers)Auction winnerProgress 20.661% (as of September 2024)Progress 50.496% (as of December 2025)1Den Chai-Ngao104ITD-Nawarat Joint Venture10.44%47.618%2Ngao-Chiang Rai132CKST-DC 2 Joint Venture24.35%56.726%3Chiang Rai-Chiang Khong87CKST-DC 3 Joint Venture29.55%45.798%

Construction progress Datehttps://www.srt-denchai-chiangrai-chiangkhong.com/progress2568ProgressAdvancement byNovember 20220.52%December 20220.606%0.094%January 20230.743%0.137%February 20230.825%0.082%March 20230.925%0.1%April 20231.021%0.096%May 20231.21%0.189%June 20231.485%0.275%July 20231.789%0.304%August 20232.02%0.231%September 20232.423%0.403%October 20233.016%0.593%November 20233.773%0.757%December 20234.832%1.059%January 20245.449%0.617%February 20246.695%1.246%March 20248.054%1.359%April 20249.409%1.355%May 202411.288%1.879%June 202412.675%1.387%July 202415.264%2.589%August 202416.852%1.588%September 202418.355%1.503%October 202419.88%1.525%November 202421.579%1.699%December 202423.99%2.411%January 202525.785%1.795%February 202528.182%2.397%March 202531.974%3.792%April 202533.72%1.746%May 202536.067%2.347%June 202538.341%2.274%July 202540.295%1.954%August 202541.986%1.691%September 202543.984%1.998%October 202546.112%2.128%November 202548.62%2.508%December 202550.496%1.876%January 202653.421%2.925%February 202656.461%3.04%March 202659.57%3.109%

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