BANGKOK — Thailand’s State Railway (SRT) has launched a new phase of planning for the long-delayed Red Line commuter rail extension between Wo Wai Yai and Mahachai, a 33-kilometre project aimed at improving regional connectivity. The study, awarded to a consortium led by Tesco Co., Ltd., is expected to be completed by August 2026, clearing the way for cabinet approval and construction in 2028.
The consortium, which includes Tesco Co., Ltd., MHP Management Co., Ltd., MAA Consultant Co., Ltd., and Decade Consultant Co., Ltd., was awarded a contract worth 135 million baht to update the feasibility study, develop detailed design plans, conduct a new Environmental Impact Assessment (EIA), and prepare tender documents. Work officially began on May 30, 2025, with a 450-day timeline.
This section is part of a larger proposed 37-kilometre expansion of the Red Line from Hua Lamphong through Wo Wai Yai to Mahachai, listed in both phases of the 20-year Mass Transit Master Plan (M-Map and M-Map 2). The original elevated rail design faced EIA approval issues, particularly along the segment crossing the Chao Phraya River. As urban density has increased and concerns over land expropriation remain, planners are now reconsidering underground options for the river-crossing portion.
The current strategy focuses on first constructing the Wo Wai Yai–Mahachai segment, which has already been approved by Thailand’s Traffic and Transport Policy Committee (TTPPC) and is proposed as an entirely elevated route. Once the review is complete, further clarity is expected regarding how to handle the Hua Lamphong–Wo Wai Yai stretch, with tunnel alternatives under consideration to minimize community disruption and increase the likelihood of EIA approval.
Pending Ministry of Transport endorsement, the project will be presented to the Cabinet in 2026. If approved, the tender process for contractors would take approximately eight months, allowing for a construction start before the end of 2028. The project is projected to take four years, with service beginning around late 2032.
Once completed, the Red Line extension will significantly improve commuter links between western suburbs and central Bangkok. It will connect to the Purple Line (Tao Poon–Rat Burana) and the Silom Green Line at Wo Wai Yai Station, providing seamless access across the metropolitan rail network.
