Pita Limjaroenrat (center, white shirt), leader of Move Forward Party, waves to his supporters, in Bangkok, May 15, 2023. (PHOTO / AP)

BANGKOK - Thailand's two main opposition parties agreed on Monday to form a ruling coalition after they won the country’s parliamentary elections over the weekend. 

The Move Forward party and opposition heavyweight Pheu Thai dominated Sunday's ballot, but they could face challenges in mustering enough support from the Senate, which gets to vote on the prime minister in a bicameral sitting of the 750-member legislature.

Pita Limjaroenrat, Move Forward's 42-year-old leader on proposed an alliance of six parties that would command 309 seats, with him as prime minister. That would be short of the 376 seats needed to ensure he was elected to the top job.

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Asked about the upper house Senate, he said all sides must respect the election outcome and there was no use going against it.

On Monday, Pita did a victory lap in Bangkok where thousands of supporters had gathered - some in the streets, others on rooftops - dressed in Move Forward's signature orange color and chanting "Prime Minister Pita"

"I am not worried but I am not careless," he told a press conference.

"It will be quite a hefty price to pay if someone is thinking about debunking the election result or forming a minority government."

Pheu Thai, controlled by the billionaire Shinawatra family said it agreed with Pita's proposal and wished him luck in efforts to become prime minister.

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The party had won most seats in every election this century, including twice in landslides, but met its match against Move Forward as it came close to a sweep of the capital Bangkok and made gains in rivals' strongholds.

"Pheu Thai has no plan to form any other government," party leader Chonlanan Srikaew told a press conference.

Pita Limjaroenrat (center, white shirt), leader of Move Forward Party, waves to his supporters, in Bangkok, May 15, 2023. (PHOTO / AP)

Move Forward was galvanized by a wave of excitement among the youth over its liberal agenda and promises of bold changes.

On Monday, Pita did a victory lap in Bangkok where thousands of supporters had gathered - some in the streets, others on rooftops - dressed in Move Forward's signature orange color and chanting "Prime Minister Pita".

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Student Pirag Phrasawang, 22, said he was "overwhelmed and excited to see change finally come to the country".

"My voice has been neglected for a long time. I'm glad that people finally woke up and responded to Move Forward's policies."