A dual-track rail project linking Prachuap Khiri Khan and Chumphon provinces won approval from the cabinet on Tuesday, with at least three more lines on the horizon.
The cabinet gave the State Railway of Thailand the go-ahead on the project to add another track on the southern line. Investment in the 167km section is estimated at 17 billion baht.
Transport Minister Arkhom Termpittayapaisith said e-bidding will commence by August and the project could start a month after with an eye toward completion by 2019.
Most train lines in the country run on a single track and the SRT plans to expand them to dual tracks on main routes to ease congestion and speed transit times.
Mr Arkhom said the ministry will seek cabinet approval of three more projects with construction expected to start by the end of this year.
They are the dual-track project from Map Krabao in Saraburi to Jira Junction in Nakhon Ratchasima, Nakhon Pathom to Hua Hin, and Lop Buri to Pak Nam Pho in Nakhon Sawan.