The Public-Private Partnership (PPP) Committee has asked the Transport Ministry and the State Railway of Thailand (SRT) to submit the completed feasibility study for a 152-billion-baht high-speed train on the Bangkok-Rayong route at the panel's next meeting.
The committee will then consider plans to fast-track the rail route under the PPP scheme.
The feasibility study for high-speed rail projects will be finished in March, said Porametee Vimolsiri, secretary-general of the National Economic and Social Development Board.
The committee asked the Transport Ministry and the SRT to devise a clearer plan on the train's routing and the format of private investment in the project before submitting the proposal to the committee at the next meeting, Finance Minister Apisak Tantivorawong said after chairing Wednesday's meeting.
The Transport Ministry has pushed to include the 194-kilometre high-speed rail route between Bangkok and Rayong in the PPP fast-track scheme, along with high-speed rail for Bangkok-Hua Hin as well.
Under the PPP fast-track scheme, the approval process for joint investment is shortened to eight and a half months from two years under the normal process.
"The Transport Ministry informed the meeting that it is conducting the feasibility study and has made a lot of progress," Mr Apisak said.
The ministry is studying three models for private investment in the project -- the private sector invests in the entire project; the private sector invests in the train system, while the government takes responsibility for the infrastructure; or the government invests in both the train system and the infrastructure, while the private sector takes charge of providing service.
If high-speed rail for Bangkok-Rayong is put on the PPP front burner, it will be the sixth such project.
Five projects worth a combined 334 billion baht have already been fast-tracked and include three mass-transit routes in Bangkok and two intercity highways.
The 56.7-billion-baht Pink Line (Khae Rai-Min Buri) and the 54.7-billion-baht Yellow Line (Lat Phrao-Samrong) will seek approval for joint investment from the PPP Committee by next month and go before the cabinet in March.
The Blue Line extension (Hua Lamphong-Bang Kae and Bang Sue-Tha Phra) will seek committee approval by April and go to the cabinet by May.
The 84.6-billion-baht Bang Pa-in-Nakhon Ratchasima motorway and the 55.6-billion-baht Bang Yai-Kanchanaburi motorway are expected to complete an initial study and analysis to test private-sector interest next month.
The PPP Committee is expected to green-light those projects by June before seeking cabinet approval by July.
The government is pinning its hopes on public investment in big-ticket infrastructure projects to help rev up private investment and take the place of exports as the main engine of the Thai economy.
The government has set a target of boosting private investment growth to 10% this year after a study found it in a downward trend.
Increasing investment by that amount is expected to raise GDP growth to 5% and eventually solve the middle-income trap.
From 2000-05, Thailand's private investment grew by an average of 9% a year, pushing GDP growth to 5.3%. But investment growth dropped to 2% from 2006-14, resulting in GDP growth of 3.4%.
A source on the PPP Committee said private firms had yet to show any interest in high-speed rail investment due to its low rate of return.