The government has given agro-industrial conglomerate Charoen Pokphand Group (CP) until next Tuesday to sign an investment agreement for the 225 billion baht high-speed train project after wining the bidding, or face blacklisting.
The railway, a private-public partnership, will connect Suvarnabhumi airport, Don Mueang airport and U-Tapao airport in Rayong.
Deputy Prime Minister Anutin Charnvirakul announced the deadline on Thursday, adding that CP's tender for the project was 60 billion baht lower than the nearest competitor's.
CP Group and its consortium of 12 other companies won the bidding for the project in May, beating out a consortium led by mass transit operator BTS Group Holdings Plc.
Since then, the company has been negotiating with the State Railway of Thailand on terms of the agreement including land ownership.
"On Oct 15, CP Group should sign the contract because if they don't they will be blacklisted by the government," Mr Anutin said.
Failure to sign would mean other companies in the CP bidding group - including Bangkok Metro Expressway and Metro Plc, Italian Thai Development Plc, CH Karnchang Plc and China Railway Construction - could also be affected in future government projects.
"I think there will not be a problem in signing," acting governor of State Rail of Thailand, Worawut Mala, told Reuters.
There were land transfer concerns because of utility infrastructure that involved other agencies, but after meetings there were no problems, he said, adding that the government was ready to support the project.
CP Group, owned by Thai billionaire Dhanin Chearavanont, has business interests in agriculture through CP Foods Plc, telecommunications in the China-mobile backed True Corporation Plc, and the Ping An Insurance Group.