The period of free travel on the Blue Line between Tao Poon and Charan 12 stations will be extended until March 29, the MRT operator announced on Wednesday.
Bangkok Expressway and Metro Plc said free travel on the new section of the Blue Line from 10am-4pm and 6pm-midnight began on Dec 23 and was to end on Feb 15.
It would now be extended until March 29.
The new service, part of the extended line that terminates at Tha Phra, will be officially opened on March 30.
The operator said it hoped that extending the free service would encourage more people to leave their cars at home and use public transport, which would reduce pollution in the capital.