Transport Minister Saksayam Chidchob said he expects the toll-gate payment system called M-Flow to soon attract six million user vehicles as it expands.
Mr Saksayam said the barricade-free M-Flow system has been available since Feb 15 on Motorway 9 (Bang Pa-In-Bang Phli) at the gates of Thap Chang 1, 2 and Thanyaburi 1 and 2.
About 1.6 million motorists have used the payment system so far, he said.
The M-Flow system is a post-paid system that supports various types of payment methods including credit cards, debit cards and bank accounts that members can set up if they want to pay on every first or 16th day of the month.
Non-members can choose to pay the fee via internet banking or by cash up to seven days after each time they pass a toll gate.
Mr Saksayam said the M-Flow service's growing popularity should see it soon reach the ministry's target of six million registered user vehicles.
The Expressway Authority of Thailand (Exat) will also soon have the M-Flow system available at three toll gates for the Chalong Rat Expressway (Ramindra–At Narong Expressway) -- Chatuchot, Sukhaphiban 5-1 and Sukhaphiban 5-2.
The system is about 90% complete and will be available in June, the minister said.
Mr Saksayam has also ordered the Department of Highways (DoH) and Exat to widely promote the benefits of the M-Flow system among motorists.
Owners of all types of vehicles including lorries, public buses and public vans are also encouraged to use the new payment system, he added.
DoH continues to promote the M-Flow system by offering vouchers and discounts including a 60-baht e-coupon to be used at 7-11 stores.