Businesses are urging the government to clarify private-sector participation in the development of major rail projects linking Bangkok with Chiang Mai and Rayong.

They are confused about whether the Chinese government will be allowed to invest in the two lines. China has already committed to a joint investment in the Nong Khai-Bangkok-Padang Besar route.

The Thai government needs to confirm whether it will open international bidding on the two projects, as many countries have expressed interest such as Japan, they say.

The 750-kilometre Bangkok-Chiang Mai route is estimated to cost 250 billion baht and the 220-km Bangkok-Rayong line 150 billion. China has said it is interested in investing in the Bangkok-Rayong route.

Deputy Prime Minister Trairong Suwannakhiri, as chairman of a committee promoting the role of public-private-partnerships (PPPs), said private firms also want the Bangkok-Rayong route extended all the way to Trat province to facilitate trade with Cambodia.

They say the return on investment would be higher due to the greater volume of goods and passengers.

The Transport Ministry has been tasked with studying the feasibility of both routes. Japan is assisting with the study. The committee is also considering a draft PPP law to replace the Public Private Investment Act of 1992.

Tharadol Piempongsan, a deputy secretary-general to Prime Minister Abhisit Vejjajiva, said the present Act required about four years on average to process joint public-private investments.

The government wants that shortened to seven months excluding the time needed to conduct environmental and health impact assessments.