The leader of the Move Forward Party (MFP) said on Sunday evening he expected to form a coalition government with the Pheu Thai Party, enabling the former opposition bloc to rise to power.
MFP leader Pita Limjaroenrat said exit polls suggested that MFP and Pheu Thai could have enough House seats to form the next government.
“This is a positive sign," he said. "It’s time for Thailand to change."
Asked when he would discuss a possible coalition with Pheu Thai, Mr Pita said he expected a conversation to start at around 10 or 11pm.
“A collaboration of the (former) opposition parties is the perfect way to deal with the challenges the country faces. We will change Thailand together,” the MFP leader said.
In a message on the party's Facebook page, Move Forward said: "Thank you for the trust that the people have given us today. From now on, the Move Forward Party will push forward progressive policies and build the Thailand that we dream of together, as quickly as possible."
Harvard-educated Pita, 42, said the formation of a governing coalition would be subject to a memorandum of understanding and conditions.
He ruled out the possibility of forming a government with the United Thai Nation (UTN) Party of Prime Minister Prayut Chan-o-cha and the Palang Pracharath Party (PPRP) of Deputy Prime Minister Prawit Wongsuwon.
However, the Move Forward leader did not exclude the possible participation in a coalition by the Bhumjaithai Party of Deputy Prime Minister and Public Health Minister Anutin Charnvirakul.
Meanwhile, Pheu Thai prime ministerial candidate Srettha Thavisin said on Sunday night that his party was the leader in the polls, not the MFP, and he was confident that the Thaksin-linked party would be the winner.
He said Mr Pita had not yet phoned Pheu Thai but when it was time to discuss partnerships, Pheu Thai would prioritse talks with parties with a similar political stance.
Mr Srettha also said he was disappointed with Pheu Thai’s performance in constituency elections in Bangkok.
MFP was likely to win the most House seats representing the capital.
