Bhumjaithai Party ministers were conspicuously absent from Tuesday's cabinet meeting, which was due to discuss a 30-year extension of the Green Line railway concession with the maximum fare set at 65 baht.
Absent were Deputy Prime Minister and Public Health Minister Anutin Charnvirakul, the Bhumjaithai leader, Transport Minister and Bhumjaithai secretary-general Saksayam Chidchob, Deputy Interior Minister Songsak Thongsri, Tourism and Sports Minister Phiphat Ratchakitprakarn, Deputy Agriculture and Cooperatives Minister Mananya Thaiset and Deputy Education Minister Kanokwan Wilawan.
Mr Anutin and Mr Saksayam had earlier opposed the proposed concession extension.
Mr Songsak said they were concerned about some legal issues relating to the extension of the concession, and the Bangkok Metropolitan Administration (BMA) would have to resolve them first.
Traisuree Taisaranakul, an assistant government spokeswoman from Bhumjaithai, said Mr Anutin and Mr Saksayam had filed their leave letters in advance of the meeting, and Mr Phiphat was quarantined after returning from abroad.
Responding to the coalition party's absence, Deputy Prime Minister Prawit Wongsuwon, leader of the coalition-core Palang Pracharath Party, said the government would have to consider what it should do next.
The matter was withdrawn from Tuesday's cabinet agenda.
The Green Line is owned by the BMA, and the concession operator is the Bangkok Mass Transit System Plc (BTSC).
The Interior Ministry had proposed that the current Green Line concession be extended from 2029 to 2059. The proposal also sets the maximum fare for the Green Line at 65 baht.
The proposal has sparked public debate, with consumer groups arguing that allowing fares to rise to 65 baht would put Bangkok's electric train system out of reach of the average commuter.
The Thailand Consumers Council has called on the government to reject the BMA's plan.
The TCC said allowing fares on the Green Line to rise to 65 baht a trip would add to the commuting public's financial burden.
The BMA is looking to offer current operator BTSC a 30-year extension to operate the main section. In exchange, BTSC would have to shoulder BMA's debt of almost 100 billion baht.
The current concession expires in 2029.