It runs from and to the outskirts of the city during the rush hour, and the passenger number is high.

The two stretches are separated by the Tha Chin River at Samut Sakhon.

Part of the Mass Rapid Transit Master Plan in Bangkok Metropolitan Region, it consists of two lines, the Dark Red Line) running from Thammasat University's Rangsit campus to Maha Chai in Samut Sakhon Province, and the Light Red Line running from Sala Ya in Nakhon Pathom Province to Hua Mak in Bangkok, with both passing through Krung Thep Aphiwat Central Terminal which acts as a connecting hub to the MRT system at Bang Sue.

Segments running through inner-city areas are elevated, and the system is electrified by overhead lines.

The system is owned and is being developed by the State Railway of Thailand.