[4] A much delayed 15 km (9.3 mi) western extension of the line from Taling Chan to Salaya was due to be tendered in June 2022.

[6] When fully completed, the line will run east–west from Salaya, Thailand in Phutthamonthon District of Nakhon Pathom Province to Hua Mak railway station in Bangkok.

The line will be extended 14.8 km (9.2 mi) west to Sala Ya in Phutthamonthon District of Nakhon Pathom Province.

Contracts for construction of the initial section from Taling Chan to Bang Sue were awarded by the SRT on 29 September 2009.

[9] Construction started in early 2010 after some site access delays related to slum dwellers who had been residing various sections of SRT land for many years.

Works progressed well but were thereafter delayed for a few months due to the late 2011 floods in Bangkok with floodwaters inundated on parts of the route.

[12] Effective 13 January 2014, all services were suspended until electrification works could be completed and rolling stock procured which was expected to be by the end of 2018.

[19] This left the MHSC Consortium (consisting of Mitsubishi Heavy Industries, Hitachi, and Sumitomo Corporation) as the sole bidder qualified for the contract.

The MHSC Consortium argued that their bid reflected 2013 prices after the national minimum wage increase from 1 January 2012.

In late September 2019, the first 2 sets of rolling stock were shipped from Japan[22] and both arrived in Thailand at Laem Chabang port on 12 October 2019 for shipment to Bangkok.

SRT long distance trains on the Southern Line terminating at Krung Thep Aphiwat share the same tracks.

[32] In November 2022, the SRT introduced regular DMU services from Thonburi via Taling Chan to Nakhon Pathom to connect with the Light Red line.

[34] However, the 15 km (9.3 mi), 4 station western extension Taling Chan to Salaya was due to be tendered first by September 2018[35] and then slated for the 2nd half of 2019.

On 10 February 2021, the Department of Railways announced that in April 2021 the SRT would issue the tenders for the west extensions to Salaya and from Taling Chan to Siriraj.

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 (with 50 year leases) in July 2023.

[6] Construction segments based on M-Map:[42] The SRT Light Red Line is planned to be extended by 14.8 km (9.2 mi) west to Salaya.

[37] Two additional infill stations, Rama 6 bridge and Bang Kruay (EGAT) on either side of the Chao Praya river, were part of the original plans but deferred until ridership grew [45] will be tendered as part of the 15 km Salaya western extension tender.