The line is now 48km long with 38 stations. The line forms a loop around Bangkok and runs from Tha Phra north via Tao Poon, Bang Sue, Chatuchak Park and Lat Phrao in northern Bangkok before turning south to run via Phetohaburi and Sukhumvit along the eastern side of the city. The line then turns west passing through Silom, Hua Lamphong mainline station, Tha Phra and Bang Wa to Lak Song.

The Blue Line interchanges with the Purple Line, the Silom and Sukhumvit lines, and the Suvarnabhumi Airport Line.

Siemens Mobility and ST Electronics, Thailand, were responsible for supplying an integrated rail system for the extension under a contract awarded by MRTA, Bangkok Expressway and Metro (BEM) and C H Karnchang.