Thailand’s Mass Rapid Transit Authority (MRTA) is set to commence tunnel boring operations on August 4, 2025, for the third underground contract of the southern extension of the MRT Purple Line, connecting Tao Poon to Rat Burana (Kanchanaphisek Ring). The launch marks the final phase of tunnel boring under this section of the project.
The third contract, spanning 3.12 kilometers from Phan Fa to Phuttha Bridge Station, will deploy two tunnel boring machines (TBMs). The first TBM will begin with the northbound tunnel toward Democracy Monument Station. The second machine, assigned to the southbound tunnel, is expected to start operation roughly two months later. The tunneling work under this contract is projected to take approximately one year, with completion expected in July 2026.
A significant feature of this section includes a 200-meter tunnel segment passing beneath the Chao Phraya River. Boring under the river is scheduled to begin in November 2025 and is expected to take 10 to 15 days. Due to the dense urban landscape, this segment will be excavated at a depth of around 40 meters—10 meters deeper than similar tunnels on the MRT Blue Line extension.
The entire southern extension of the Purple Line covers 23.63 kilometers, including 14.29 kilometers of underground tracks. Tunnel boring is distributed across four of the six construction contracts, utilizing a total of seven TBMs. Contracts 1 and 2 use three machines, while contracts 3 and 4 each employ two.
As of the latest construction update, the project has reached 57.36% overall completion. Individual progress includes 72.90% for Contract 1, 63.18% for Contract 2, 53.15% for Contract 3, 57.62% for Contract 4, 34.64% for Contract 5, and 40.98% for Contract 6, which covers rail systems and trackwork along the full route.
The entire construction is expected to conclude by October 2027, with the full Purple Line extension anticipated to open to the public in 2029, pending operational preparations.
Deputy Prime Minister and Minister of Transport Suriya Jungrungreangkit will preside over the August 4 ceremony at the Phuttha Bridge tunnel launch site.
