The Red Line rail project will commence a "soft" launch of its services on Aug 2 and will allow commuters free rides for three months, Transport Minister Saksayam Chidchob says.
The launch of the new service was postponed from March.
The Red Line will cover the greater Bangkok area, running from Thammasat University's Rangsit campus to Bang Sue and Taling Chan.
Prime Minister Prayut Chan-o-cha will preside over the service's launch ceremony on Aug 2.
The Red Line will collect distance-based fares ranging from 15-42 baht, although it has yet to confirm the precise fares for each trip.
Transport Ministry is planning to coordinate with the Expressway Authority of Thailand (Exat) and the Mass Rapid Transit Authority of Thailand (MRTA) to provide shuttle buses to connect with the Red Line railway project to help mitigate travel plans affected by the revision of Hua Lamphong's routes.
Mr Saksayam has also instructed the State Railway of Thailand to move ahead with its plan to source contractors to build the extensions, so the line's construction can be completed by 2025.
The four extensions are the 10.2-billion-baht Taling Chan-Salaya section; the 6.57-billion-baht Rangsit-Thammasat extension; and the 6.64-billion-baht Taling Chan-Siriraj section; and the 44.1-billion-baht "missing link" project connecting Bang Sue to Hua Lamphong.
In another development, commuters on BTS electric trains can use government subsidies to help pay their fares.
Surapong Laoha-Unya, chief executive officer of Bangkok Mass Transit System Plc, said yesterday that beneficiaries of the Khon La Khrueng (Half-Half) co-payment scheme and holders of government welfare cards could spend respective government subsidies on the company's sky train fares from Thursday onwards.