Move Forward Party (MFP) leader Pita Limjaroenrat has vowed to push for a bill seeking to legalise same-sex marriage and improve gender equality after forming a government.
Writing on Facebook, Mr Pita, the party's prime minister candidate, said: "Once we can form a government, we will push for the passage of the [MFP's] marriage equality bill within 100 days."
"It is also part of a memorandum of understanding signed by members of the [prospective] coalition," he posted.
The coalition, consisting of eight parties, signed an MoU agreeing on a joint policy platform on May 22, which includes a pledge to pass the marriage equality bill to ensure equal rights for all couples regardless of gender.
"There are also several other policies which Move Forward will push as executives of ministries and as members of the legislative branch in the House of Representatives to promote gender equality in Thai society," Mr Pita wrote.
"Every person has human dignity and is equal before the law," he added. "They must have equal access to public services without discrimination because of their gender, race, belief, education, age, and disabilities."
Mr Pita made similar remarks on Sunday when he joined a Pride Parade in central Bangkok, which drew thousands of LGBTQIA2S+ people, their supporters as well as other political figures.
Parit Wacharasindhu, MFP list-MP elect, tweeted on Monday that the bill will not only promote gender equality but also open a host of financial, tax and inheritance benefits for members of the LGBTQIA2S+ community.
According to the MFP, the marriage equality bill will aim to amend Section 1448 of the Civil and Commercial Code, which limits the definition of marriage to a man and a woman, by making the marriage law applicable to any couple, regardless of gender.
The bill passed its first reading in parliament in June of last year, but it stalled during its second reading due to several problems, including a delay to make way for the deliberation of other bills, as well as repeated cancellations of House meetings caused by a lack of a quorum.
Deliberation of the bill was suspended further when the previous House's final session ended on Feb 28.
However, if the MFP forms the government, it may ask the newly elected House to resume deliberation of the bill, according to observers.