[4]The line runs eastward from National Stadium Station in Pathum Wan District over Rama I Road and interchanges with the Sukhumvit Line at Siam station, then turns southward, following Ratchadamri, Si Lom, Naradhiwas Rajanagarindra and Sathon Roads to Taksin Bridge where it crosses the Chao Phraya River to the Thonburi side of Bangkok and Wong Wian Yai.

Several changes were made during the construction as follows:[7] On 18 October 2005, with no approval from the central government forthcoming, Bangkok Metropolitan Administration (BMA) decided to fund and complete the 2.2 kilometers (1.4 mi) Silom Line route extension to Krung Thon Buri and Wongwian Yai Stations.

However, problems with the tendering and installation of a new Bombardier open signalling system repeatedly pushed back the schedule.

[8] The extension was initially operated by a separate six-car shuttle service due to the absence of a turnout between Wongwian Yai and Talat Phlu stations.

In 2018, it was decided to finally build the missing Saint Louis station (originally named Sueksa Witthaya), the EIA was finalised in March 2019.

The BMA Transport and Traffic Office completed an economic evaluation of the extension in October 2018 which found a cost benefit ratio of 2.37.

Once the extension to Taling Chan is built the BMA has canvassed the possibility of a further future extension north to connect with the MRT Purple Line at Rattanathibet Road extended the form Taling Chan by seven station to Bang Rak Noi It Station 10 km (6.2 mi).

Type (single) •  Mine Smart Ferry •  CHAOPHRAYA EXPRESS •  MRT , via 270-metre underground walkway (under construction)•  SRT  (future) • Ratchaphruek station for Bangkok BRT•  MRL  (south section; future) • Mae Klong Railway (Wongwian Yai - Mahachai)•  SRT  (future) •  MRT • Khlong Phasi Charoen Boat Service The Silom Line operates from 06:00 to 24:00 every day with some through-running trains to/from Mo Chit station on the Sukhumvit Line.