Prime Minister Srettha Thavisin said the changes would strengthen family structures, and parliament is now expected to debate the measures as early as Thursday.
The legislation has several more hurdles to clear before it becomes law. But if it does, Thailand would be the first country in Southeast Asia to recognize same-sex marriage.
"This law will allow people to marry and have the same rights and responsibilities as couples who are men and women," Srettha told reporters after the cabinet meeting.
"I would like to congratulate everyone."
The proposal would amend references to "men", "women", "husbands" and "wives" in the marriage law to gender-neutral terms, deputy government spokesman Karom Pornpolklang said.
Thailand has a reputation for tolerance, but much of the Buddhist-majority country remains conservative and the LGBTQ community, while highly visible, still faces barriers and discrimination.
In 2022 Thai lawmakers gave initial approval to two bills that would allow same-sex marriages and two others that would permit civil partnerships.
But the legislation was dropped when parliament was dissolved to pave the way for a general election held in May.