Business leaders agree with the government that public-private partnerships (PPPs) should be applied for massive infrastructure projects to ease concerns about public debt.
However, the government has yet to come up with any clarity on the role of the private sector in its capital-intensive plans, said Pramon Sutivong, president of the Anti-Corruption Organisation of Thailand and former chairman of the Thai Chamber of Commerce.
"The government should carefully handle such development projects, while related agencies should help to screen their appropriateness, see whether they are good for the overall economy and meet public demand," he said.
Mr Pramon said PPPs will make the projects more viable, as the private sector will share the burden.
The government plans to build four high-speed train lines from Bangkok to provincial areas as part of a 2-trillion-baht infrastructure investment.
The high-speed projects will be built in phases, with only the Rayong-Pattaya route likely to be constructed in one stage.
Construction of the first phase of the four routes - Bangkok-Phitsanulok, Bangkok-Hua Hin, Bangkok-Rayong and Bangkok-Nakhon Ratchasima - is expected to be completed by 2019.
Transport Minister Chadchat Sittipunt said the government already plans to allow the private sector to play a part in the construction of the routes.
The ministry is considering appropriate methods for the partnership.
Different methods are used around the world for high-speed train projects. For instance, Taiwan's government has invested in both civil works and operations, while Japan's has invested in civil works while allowing private companies to handle train maintenance and operation.
The ministry will soon organise a workshop involving relevant agencies to seek appropriate technology.
Bids for technology will be postponed to next year from the previous plan of this year's third quarter.
Mr Chadchat said the high-speed trains will boost the country's economic growth, particularly upcountry.
"Revenue from passenger fares will not be the main revenue," he said.
"The major contribution will stem from growing business activities such as property development, as has happened in many countries including Japan."
The Fiscal Policy Research Institute said the government's massive investment plan will help to raise annual per-capita income from US$5,600 (166,000 baht) to $10,000 within 10 years.
The increase would push the economy out of the middle-income trap, a situation in which a country's growth plateaus and eventually stagnates after reaching middle-income levels.
The plan would inject about 300 billion baht into the economy each year, which could contribute a 0.5% to 1% lift to gross domestic product (GDP).
Such a boost would see real GDP growth rise to between 5.5% and 6% and nominal growth, which accounts for inflation, to 8%.
The plan to borrow 2 trillion baht to finance the infrastructure projects should be endorsed by parliament in November.