River in the area of Amphoe Mueang Samut Sakhon, Samut Sakhon Province. Its total length is about 30 km (19 mi). Sanam Chai is the name given to Bangkok portion of the canal, which is known as Mahachai in Samut Sakhon.

For the Khlong Dan part, it is believed that it is a natural canal that has existed since the Ayutthaya period. In the part of the Khlong Sanam Chai or Khlong Mahachai is a canal that was excavated in the King Sanphet VIII's