The Expressway Authority of Thailand (Exat) has set out a plan to develop two expressways in Bangkok and another in Phuket between this year and the next.
The first project concerns the Rama III Road-Dao Khanong-Western Outer Ring Road Expressway, stretching 17km.
Exat governor Narong Kieddej said the 31.2-billion-baht project would form an effective road link between the inner city and outer areas of Bangkok.
The project would help address traffic congestion on Rama II Road and Chalerm Mahanakhon Expressway's Bangkhlo-Dao Khanong section, he said.
The project will be tabled at a cabinet meeting for approval by next month and construction could begin in June, a month later than scheduled, Mr Narong said.
The second project involves a 3.9km special expressway linking Kathu and Patong in Phuket. The 10-billion-baht project is currently going through an environmental impact assessment (EIA).
Once it passes the process, bidding for the project could be launched immediately, according to Mr Narong.
An Exat source said the Phuket expressway runs from Patong to Phisit Koranee Rd, and then goes through a 1.9km six-lane tunnel under Nakkerd mountain and heads to tambon Kathu. Construction is planned this year and it is expected to be completed in 2021.
Another project concerns the third-phase expressway's northern section in Bangkok from the Kasetsart intersection to Nawamin Road, also known as the N2 section, stretching 9.2km.
Mr Narong conceded the landscape along the route has extensively changed and it needs to be reviewed.
The project is likely to be forwarded to the cabinet for approval next month, with construction starting next year.
The Exat governor conceded another two sections (N1 and N3) are unlikely to come about since it would affect many local residents.
The N1 would run from the Bang Yai intersection in western Bangkok to the Kasetsart intersection over a distance of 19.2km and the N3 would link Nawamin, Seri Thai and Ramkhamhaeng roads over a distance of 11.5km.
"The N3 route originally involved a vacant swathe of land, but it now serves housing estates. The land expropriation cost could double to eight billion baht if the land reclamation proceeds," said Mr Narong.