Leaders of the Pheu Thai and Bhumjaithai parties, with 212 seats in total, announced on Monday they would try to form a new coalition governent.
Pheu Thai leader Cholnan Srikaew said he was grateful for Bhumjaithai's agreement to join Pheu Thai "to solve people's problems and national crises, especially those concerning the constitution".
"The 212 votes of Pheu Thai and Bhumjaithai will be the base for the government's formation and there will be more, to provide majority support in the House. So, there are no worries about the possibility of a government with a minority of votes," Dr Cholnan said.
Pheu Thai came second in the May 14 general election with 141 House seats, followed by Bhumjaithai with 71.
Dr Cholnan confirmed that Srettha Thavisin remained Pheu Thai's candidate for prime minister.
The Pheu Thai leader confirmed the new coalition would not include the election-winning Move Forward Party. Other parties and senators would not support a coalition government if it included Move Forward, Dr Cholnan said.
The Move Forward Party won 151 seats in the general election, but its efforts to form an eight-party coalition government, including Pheu Thai, collapsed through lack of support from other parties in the parliament and especially not from the Senate.
Dr Cholnan did not give the names of other potential coalition parties.