The government on Wednesday maintained its pressure on the Charoen Pokphand Group (CP)-led consortium to sign the contract to build a 224-billion-baht high-speed railway linking three airports.
The project will link Bangkok's Don Mueang and Suvarnabhumi with U-tapao airport in Rayong.
Deputy Prime Minister Anutin Charnvirakul on Thursday insisted that an unidentified party must "play by the rules".
"Who actually is attempting to take advantage of the government? Who is attempting to avoid following the results of the bidding? Who actually is asking for relaxation of the bidding rules for his own benefit?" Mr Anutin wrote on Facebook.
"Follow the rules announced right from the beginning by the government, stop lobbying and bring a pen to sign the contract," he added.
His message came as Transport Minister Saksayam Chidchob revealed yesterday that the committee in charge had on Tuesday postponed the contract signing deadline from Oct 15 to Oct 25 to allow time to appoint a new State Railway of Thailand board.
Mr Saksayam denied the delay was meant to pressure the consortium, as its winning bid was valid until Nov 7.