The Elevated Train in Commemoration of HM the King's 6th Cycle Birthday First line (Sukhumvit) or Sukhumvit line is an elevated metro rail line of the BTS Skytrain in Bangkok, Thailand. From the central Siam Station, where it connects with the Silom Line, the line runs both northwards along Phaya Thai and Phahon Yothin Roads to Mo Chit station in Chatuchak District, and eastwards along Rama I, Phloen Chit and Sukhumvit Roads, through Bang Na District to Kheha Station in Samut Prakan. Daily ridership (2019) is 740,000 passengers per day. When the line first opened in December 1999 it consisted of seventeen stations from Mo Chit to On Nut, currently there are 31 stations in operation. The line is represented on the official BTS map in light green.
A northern extension to the Sukhumvit Line, also known as the Green Line (sections 1 and 2) are currently under construction:
1) Mo Chit station to Saphan Mai: 11.4 km, 12 stations (N9–N20)
2) Saphan Mai to Khu Khot: 7.5 km, four stations (N21-N24)
An 11.4 km, 11 station northern extension from Mo Chit station to Saphan Mai in Don Mueang District has been planned since the Sukhumvit line opened. Originally, this extension was scheduled to be completed by 2008. However, due to a combination of changes in government, a prolonged environmental study, and problems with locating a suitable train depot the extension has been continually delayed. A further 16.5 km, nine station extension from Saphan Mai to Lam Lukka was also planned once the extension to Saphan Mai had been completed.
After multiple delays, in mid-2013 a decision was made to tender extension (1) and (2) at the same time, by the end of 2013. However, the dissolution of parliament in November 2013 delayed this yet again. A tender was finally released in January 2014 with an April deadline before being delayed until late May 2014 due to concerns from bidders. A military coup in late-May 2014 suspended the bidding process whilst the military administration reviewed all major projects. In late June, the military administration affirmed the tender will proceed before the end of 2014. In August 2014, the MRTA announced that the new tender deadline will be 30 September 2014. Five bidders qualified and the successful bids were announced in December 2014. The tender specifies a construction period of 1,350 days.
On 3 April 2015, MRTA signed four contracts for this extension:
Contract 1: Civil works of 11.4 km from Mo Chit to Saphan Mai, will be constructed by Italian-Thai Development (15,269 million baht)
Contract 2: Civil works of 7.5 km from Saphan Mai to Khu Khot, will be constructed by UN-SH-CH joint venture (6,657 million baht)
Contract 3: Civil works of Depot and Park and Ride building, will be constructed by STEC-AS joint venture (4,019 million baht)
Contract 4: Track laying and system design, will be constructed by STEC-AS joint venture (2,841 million baht)
The MRTA, contactors and Thai Traffic Police met on 2 September 2015 and confirmed construction would begin on 8 September 2015. A flyover at Kasetsart was demolished, which commenced on 12 September 2015. As of 31 December 2017, the progress of civil works construction was at 53.31% according to the MRTA. As of the end of April 2018, the MRTA stated that civil works progress had advanced to 63.27%. As of 30 September, overall construction had progressed to 78.79%.
The first section to Ha Yaek Lat Phrao station is planned to open in the second half of 2019, with the full extension currently due to open by July 2020.