Dark Red Line (Bangkok)

The SRT Dark Red Line ) is part of the SRT Red Line suburban railway system to serve the greater Bangkok Metropolitan Region running for between Krung Thep Aphiwat Central Terminal and Rangsit.
Phase I of the line opened for trial operations on 2 August 2021, with full commercial services beginning on 29 November 2021.
Tenders for the much delayed Phase II extension of the line from Rangsit to Thammasat University were opened in December 2025. Submissions to the SRT were due by 29 December 2025, with bid winners announced in January 2026 and a notice to proceed expected to be issued in March 2026 once contracts are signed. Construction is expected to take 36 months with a target to start operation by March 2029.

Route alignment

Section I of the SRT Dark Red Line starts at the new Krung Thep Aphiwat Central Terminal heading north for via Don Mueang and terminates at Rangsit in Pathum Thani Province. Section II line will then be extended north from Rangsit to the Thammasat University Rangsit campus.
From Krung Thep Aphiwat Central Terminal the line will be extended south via Phaya Thai to Hua Lamphong station in Section III. Section IV section of the line will run southeast from Hua Lamphong via Wongwian Yai for to Maha Chai in Samut Sakhon Province along the current Maha Chai railway alignment.
When fully completed, the line will run on a north–south axis through Bangkok, from Thammasat University's Rangsit campus in Pathum Thani Province to Maha Chai in Samut Sakhon Province for a full length of nearly.

History

In 2004, in conjunction with OTP, the SRT began formulating plans for a new, modern suburban network in Bangkok along existing SRT alignments to replace the existing, limited services. On 7 November 2006, the Thai Cabinet passed a resolution to approve the framework of the new network with the SRT Light Red line being DMU operations while the SRT Dark Red Line would be EMU. At the time, it was expected that the full line could be completed within 15–20 years. In February 2009, the Thai government secured a 24 billion baht loan from the Japanese Government for the initial segment of the line. The first Phase from Bang Sue to Rangsit was approved in 2010 but delayed due to a complicated 2.5 year contractual dispute.
The budget for the 1st Phase of the Dark Red Line project progressively increased due to numerous delays and further redesigns of the project. From an initial estimated 59.89 billion baht in 2007, to 75.55 billion baht in 2009 and to 80.38 billion baht in 2012. An additional requested 8.14 billion baht to increase the number of tracks increased the final budget to 88.52 billion baht.

Construction: Bang Sue to Rangsit

The, 10 station Bang Sue to Rangsit section finally started construction in May 2013 with a scheduled construction period of just over 3 years to be completed by the end of 2016. Construction works were delayed by 2 months due to site access issues for the contractor and delays related to removing slum dwellers residing within the right of way. However, it was hoped that the use of some of the old Hopewell pillars would speed up the initial construction timetable. By the end of 2013, the project was only 3% done & already months behind schedule due to a longer timetable in removing the Hopewell Pillars.
In June 2014, the SRT requested an additional 8.14 billion baht to modify the Dark Red line to 4 tracks instead of 3.Aaccordingly, redesign all stations and to provide for the longer platforms for the Bang Sue Terminal to cater for future HSR lines. 8.140 billion baht request is; 4.32 billion baht for Contract 1 ; 3.35 billion Baht for Contract 2 and 473 million baht for Contract 3.
In September 2017, civil works progress was stated to be 88.63%. By the end of September 2019 civil works were almost fully complete at 99.56% and Electrical and Signalling installation was at 45.60%. By July 2020, S&E installation was at 85.12% completion. By October 2020, 90% of the power supply for the line had been installed by the Metropolitan Electricity Authority with all installation due for completion by November 2020.
In mid-November 2020, the Minister of Transport announced that free trial operations would operate from March 2021 with full-service operations expected from November 2021. In late February 2021, the SRT confirmed that free trial operations will commence on 26 March 2021 with full commercial operations starting on 28 July 2021. However, in July 2021 the SRT again postponed the free trial operations until 2 August 2021.

Krung Thep Aphiwat Central Terminal (Bangkok's new Intercity terminal station)

Contract 1 of the project was for the construction of a new, 4 level Intercity Terminal to cater for all SRT Intercity Trains, SRT Red Line suburban trains and the yet to be built Airport Rail Link extension. The delayed contract process was finally signed in January 2013. In August 2013, the SRT sought extra funds for the project to be redesigned in order to extend upper level platforms to a 400–600 m length in order to accommodate the future planned High Speed lines.
In March 2013, the new Bang Sue Grand Station started construction. Between March and June, excavation works for the foundation of the Terminal were delayed by the unearthing of numerous World War II unexploded bombs which required safe removal by the Thai army Explosive Ordnance Teams. In July 2014, construction was 10% behind schedule.
The new station was originally scheduled to open by end of 2016 but the above-mentioned redesign work and other delays resulted in an expected 2020 opening date. In September 2017, construction progress of the station civil works was at 57.50%. By the end of September 2019 civil works were at 86.01%. By July 2020, civil works were almost complete at 99.8%.
Construction on the station was completed in August 2021.

Rolling stock

The 3rd contract for the Dark Red Line was for electrical and systems and procuring EMU rolling stock. An overhead catenary electrical system with was specified. In April 2014, only 2 bidders remained but one of the bidding consortiums was disqualified on due to the fact that one of the consortium members had convictions for bribery in an Indonesian bidding process.
This left MHSC Consortium as the sole bidder qualified for the contract. However, their bid of 28,899 million Baht was above the SRT median price of 26 billion baht which was set in 2010. The MHSC Consortium argued that their bid reflects 2013 prices after the minimum wage increase of January 2012. Finally in July 2014, after a prolonged 2-year delay in the bidding process, JICA approved the loan for Contract 3. However, the coup of May 2014 delayed finalization leading to further review and negotiations. By mid 2016, negotiations had concluded and Hitachi promised that all rolling stock for the Dark Red line would be delivered by 2020. The contract specifies 25 EMUs consisting of ten 4 car sets and fifteen 6 car sets for 130 cars in total.
In late September 2019, the first 2 sets of rolling stock were shipped from Japan and both arrived in Thailand at Laem Chabang port on 12 October 2019 for shipment to Bangkok. By March 2020, 5 sets had been delivered.
As of July 2020, 13 sets - 7 of the 6 car sets and 6 of the 4 car sets - of the total 25 sets of rolling stock had been delivered with a further 2 sets due to be delivered by August 2020. By the end of September 2020, 21 sets had been delivered - 13 of the 6 car sets and 8 of the 4 car sets - with the final 4 sets to be delivered in October.

Operation

Services operate between 5:30am to 12am. Headways are every 20 minutes except for the peak periods where services depart every 12 minutes.
The line had a flat fare of 20 Baht until 30 September 2025, when it was replaced by fares ranging from 12-42 baht, with discounts for students and seniors.

Ridership

On the first full day of free trial operations on 3 August 2021 total passengers numbered 2,914, on 4 August 2,856 passengers used the line. By the end of September, this had increased to around 4,500-5,000 passengers a day. For the first 10 months of operations to September 2022 both Red lines carried over 3.2 million passengers and services ran on time 99.45% of the time according to the SRT. By the end of September 2022, the line averaged only 309,000 passengers a month. By January 2023, the average number daily passengers rose to around 22,000 to 23,000 on weekdays. At the end of April 2023, daily weekday passengers were 4,000 for Don Mueang station and 2,500 for Rangsit station.
''Note: Passenger statistics for the Dark Red Line exclude users of the GATE EMV KTB card. The State Railway of Thailand does not publish separate figures for passengers using GATE EMV KTB cards the Dark Red and Light Red lines. As of Q4 2025, there is an average of 6,704 users on both lines.''

Future extensions

In July 2016, the Thai Cabinet approved the first section of the southern extension from Bang Sue to Hua Lamphong. However, the 4 station northern extension from Rangsit to Thammasat University will be built first.
Construction segments based on M-Map:

Phase	Segment	Length	Progress
I	Rangsit–Bang Sue		Full operation: 29 November 2021
II	Thammasat University–Rangsit		Tender December 2025
III	Bang Sue–Hua Lamphong		Planned
IV	Hua Lamphong–Bang Bon		Planned
V	Bang Bon–Maha Chai		Planned
VI	Maha Chai–Maeklong		Suggested - unlikely to be built
VII	Maeklong–Pak Tho		Suggested - unlikely to be built

Phase II Rangsit–Thammasat University

The, 4 station extension was approved by Cabinet in 2016 with an expected tender by September 2018. The extension to Thammasat University was then to be tendered in the 2nd half of 2019. However, the tender was further been delayed until 2021 as the transport minister requested that the new Department of Railways investigate conducting PPP tenders for the extension.
However, the tender has yet again been further delayed until 2021 as the Transport Minister has requested that the new Department of Railways investigate conducting PPP tenders for this extension. The decision to change the extensions to PPP projects and tender out the operation of the line with a 50 year concession was opposed by the SRT and SRT union. On 10 February 2021, the Department of Railways announced that in April 2021 the SRT would issue the tenders for the north extension to Thammasat University and the south extension to Hua Lamphong station. However, the PPP tender process was subject to further review.
In October 2021, the SRT announced that the PPP tenders would not be released until June 2022 with the aim to sign contracts for the extensions in July 2023. However, this was delayed yet again to an initial October 2022 tender release and later a December 2022 date. In late October 2022, the SRT again delayed the tender time frame to February 2023 with an aim to sign contracts by May 2023 but the time frame was contingent on new Cabinet approval of an updated budget for the extension. At the same time, the SRT decided to defer the bidding for the 50 year operation concession and new EMUs to December 2024. Once the concession is contracted the SRTET will cease to operate the line.
With the 14 May 2023 national elections and the expected time frame in the formation of a new government, it became unlikely that the tenders would be issued until late 2023. In late June, a MOT source expressed that the extension is likely be taken to Cabinet in October 2023 for approval of a new budget of 6.5 billion baht to build the extension. If approved, a tender was expected to be issued in the first quarter of 2024.
Tenders for Phase II were finally opened in December 2025, with submission due by 29 December 2025 and bidding completed by February 2026.