The Bangkok subway was built with the Japan's help and was officially opened in July 2004 by His Majesty King Bhumibol Adulyadej. Officials hoped that the subway would help to cut traffic and also pollution in Bangkok.
The Bt10 flat rate was offered until August 12 2004. From August 13 until July 3 2005, fares was ranged from Bt12 to Bt31. Some people expressed concern that many Bangkok commuters might shy away from the underground system after its promotional rate ended on August 12. The current promotional flat rate of Bt10 for the subway fare was cheaper than an air-conditioned bus.
The government wanted to merge both companies operating the subway and skytrain, as it believed this would enhance the existing railway operation and facilitate future investment. The government planned to extend the railway services by another 248 kilometres by 2010.
Building the line had been an engineering challenge, with tunnels cut deep into hard clay to avoid the soaked soil. Station entrances jut 90 cm above the pavement in order to prevent the annual flood waters streaming in.