The metre gauge Maeklong Railway consists of two separate lines running south-west of Bangkok. The first starts in Thonburi and runs to Mahachay. The second starts on the opposite bank of the Thachin river at Ban Laem and runs on to Samut Songkram on the bank of the Maeklong river.

The two lines started life as separate entities and were combined when nationalised in 1952. They are totally isolated from each other and from the rest of the national system and all rolling stock had to be transported to its destination by ship and offloaded by crane.

Running through a relatively undeveloped and isolated coastal area for the most part, the railway served an important social need but was lightly built and never carried heavy traffic. From time to time plans were announced to upgrade it so that it could provide an alternative route to the south of the country, but the condition of the railway and the cost of constructing the necessary bridges meant that they remained just plans.

Today, the railway is operated by diesel railcars and has lost much of its unique character. However, back in the 1970s it used a variety of ancient diesel power, some original, some cast-offs from the main system. Some of these are illustrated in the main diesel section.