He said that the Expressway Authority is legally bounded by the concession to approve the toll hike, or it risks a lawsuit from Bangkok Expressway, the concessionaire.
Starting from September 1, the toll rate will rise by Bt5.
Some motorists recently filed a petition to the House Committee on Transport.
Chadchart said that the ministry will try to find solutions to ease motorists' additional cost. Initially, mass transit services, particularly public buses, will be improved to accommodate more traffic.