|BTS Sukhumvit line|
|Locale||Bangkok, Samut Prakan Province, and Pathum Thani Province|
|Opened||5 December 1999|
|Depot(s)||Mo Chit, Kheha|
|Line length||37.02 km (23.00 mi)|
|Number of tracks||2|
|Track gauge||1,435 mm (4 ft 8 1⁄2 in)|
|Electrification||750V DC Third rail|
The Elevated Train in Commemoration of HM the King's 6th Cycle Birthday First line (Sukhumvit) or Sukhumvit line (Thai: รถไฟฟ้าบีทีเอส สายสุขุมวิท) 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 planned station at N6 has never been built.
|Saphan Khwai||สะพานควาย||Phaya Thai|
|Phaya Thai||พญาไท||( planned)|
|Bang Chak||บางจาก||Phra Khanong|
|Udom Suk||อุดมสุข||(proposed)||Bang Na|
|Samrong||สำโรง||(under construction)||Samut Prakan||Mueang Samut Prakan|
|Royal Thai Naval Academy
(RTGS: Rongrian nairuea)
(RTGS: Si Nakharin)
Extensions and current construction
1st extension, in operation - Construction started in August 2006 on a four billion baht, 5.25 km extension from On Nut (E9) to Bearing. The extension was funded by the BMA. The original scheduled opening date was mid-2009. However, a delay in tendering of the contract for the electrical and signalling works resulted in a two-year delay.
The extension did not open until over two years later, on 12 August 2011. The delay in opening prompted the BMA to offer free travel for this extension until the end of 2011 as compensation. An additional flat fee is charged additionally to the distance-based fare of the rest of the BTS network.
2nd extension, in operation - Construction started in April 2012 on a 12.6 km, nine station extension from Bearing station to Kheha station. The extension was funded by the MRTA as it is outside BMA city limits, Bangkok Province. Construction was contracted to take 1,350 days and the extension was originally scheduled to open by early 2017. In April 2013, the MRTA awarded Ch Karnchang the contract for track laying and electrical systems.
As of June 2014, civil works were stated to be 28.3 percent complete. In August 2016 the BMA agreed to take over the operation of the extension from MRTA. Delays over the agreement of how much the BMA should pay MRTA caused a delay in the commencement of test runs on the extension. Track works were 98% completed by November 2016. The total cost of the extension was estimated at 21.4 billion baht. In January 2017, it was announced that the opening of the extension could be further delayed to 2018-2019 due to budgetary concerns and ongoing disputes between the MRTA and BMA.
The first 1.2 km section of the extension to Samrong station (E15) opened in April 2017.
The full extension opened on December 6, 2018.
1st and 2nd extension, 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: Tracklaying 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.
|Khu Khot||คูคต||Pathum Thani||Lam Luk Ka|
|Yaek Kor Por Aor||แยก คปอ.||Bangkok||Don Mueang|
|Royal Thai Air Force Museum||พิพิธภัณฑ์กองทัพอากาศ||Sai Mai|
|Bhumibol Adulyadej Hospital||โรงพยาบาลภูมิพลอดุลยเดช|
|Saphan Mai||สะพานใหม่||Bang Khen|
|Phahonyothin 59||พหลโยธิน 59|
|Wat Phra Sri Mahathat||วัดพระศรีมหาธาตุ||(under construction)|
|11th Infantry Regiment||กรมทหารราบที่ 11|
|Royal Forest Department||กรมป่าไม้|
|Phahonyothin 24||พหลโยธิน 24|
|Ha Yaek Lat Phrao||ห้าแยกลาดพร้าว|
Future extension plans
- A further 7 km, four station extension from Kheha station to Bang Pu station is planned.
|Sawangkhaniwat||สวางคนิวาส||Samut Prakan||Mueang Samut Prakan|
- A further 9 km, four station extension east along Lam Lukka Road from Khu Khot station to Eastern Outer Ring station is planned to be constructed by 2029.
|Eastern Outer Ring||วงแหวนรอบนอกตะวันออก||Pathum Thani||Lam Luk Ka|
- Silom Line
- BTS Skytrain
- Airport Rail Link (Bangkok)
- MRT (Bangkok)
- MRT Brown Line
- MRT Blue Line
- MRT Grey Line
- MRT Light Blue Line
- MRT Orange Line
- MRT Pink Line
- MRT Purple Line
- MRT Yellow Line
- SRT Red Lines
- Bangkok BRT
- Limviphuwat, Phuwit (18 May 2019). "Mass Transit not keeping up". The Nation. Retrieved 18 May 2019.
- Groundbreaking starts on new BTS extension, Daily News, 15 August 2006
- BTS extension budget cut, Bangkok Post, 15 December 2006
- "Ch Karnchang gets Phase 2 of Bearing-Samut Prakan route" The Nation, 13 April 2013
- "BMA to postpone test run of Bearing-Samrong skytrain". Bangkok Post. Retrieved 2016-11-22.
- Reporter, Sasiwan Mokkhasen, Staff (2017-01-31). "Green Line Going Nowhere for at Least Two Years". Khaosod English. Retrieved 2017-02-25.
- Reporter, Asaree Thaitrakulpanich, Staff (2017-02-24). "First Station of Stalled BTS Green Line to Open April 1". Khaosod English. Retrieved 2017-02-25.
- "MRTA pushes to fast-track launch of South Green Line". Bangkok Post. 1 December 2017.
- http://www.prachachat.net/news_detail.php?newsid=1401076541 "รฟม.ปรับทีโออาร์หมอชิต-คูคต กลางปี59 เปิดให้บริการสายสีม่วง" Prachachat News, 26 May 2014
- https://www.mrta.co.th/th/news/information/ความก-าวหน-าการก-อสร-างรถไฟฟ-า-ณ-31-ธ-นวาคม-2560/. MRTA Press, 16 January 2018
- https://www.mrta.co.th/th/news/information/ความก-าวหน-าการก-อสร-างรถไฟฟ-า-ณ-30-เมษายน-2561/. MRTA Press, 30 April 2018
- https://www.facebook.com/MRTA.PR/photos/a.1433440196872710/2109998672550189/. MRTA Press, 12 October 2018