The government is seeking private investors' help for a 1.3-trillion-baht upgrade of its rail network aimed at reducing logistics costs and boosting trade, Transport Minister Arkhom Termpittayapaisith told Reuters on Monday.
Lowering transport costs is crucial because exports account for two-thirds of the economy.
The transport system will "place greater emphasis on rail," Mr Arkhom said in an interview, adding the country had "overly depended on roads and trucks".
"We are looking for more active participation of private investment [in rail]," he said, while ruling out the privatisation of operator State Railway of Thailand.
The projects include upgrading the network to dual-track rails. The government has already approved 123 billion baht of such upgrades, with nine more worth 407 billion baht to be approved this year, Mr Arkhom said.
In addition, bidding for a 229-billion baht, 220km high-speed rail project linking three airports, including the country's main Suvarnabhumi airport, will take place in November.
"Construction and operation is open to the private sector," Mr Arkhom said of this project, adding Chinese, Japanese and European companies had expressed interest.
Companies including energy giant PTT Plc, urban rail operator BTS Group Holdings and construction company Ch.Karnchang are also interested.
The government will invest in the project's civil work, Mr Arkhom said.
Another ambitious plan, forged with China, is a 179-billion-baht high-speed rail link stretching some 355km to connect central and northeastern Thailand with Laos.
Mr Arkhom said bidding for this project would take place before the end of the year and foreign companies could participate in construction if they were part of a Thai joint venture.
Construction of the first phase began last year after the government intervened and cleared legal hurdles.
The government signed two contracts last year worth $157 million with Chinese state enterprises for engineering and design work, which are expected to be delivered this month, Mr Arkhom said.
Another project, this time with Japan, is a 672km railway linking central and northern Thailand. Bidding on the 420 billion baht plan is expected to begin in 2020.