The marriage equality bill cleared its first reading in parliament on Wednesday in what was billed as a historic move by the sponsor.
Three related draft bills conferring differing legal status to civil unions between people across all genders were also approved.
After four hours of deliberation, the marriage equality bill passed its first reading in a vote of 210 to 180 with four abstentions. The bill was sponsored by the Move Forward Party (MFP).
Three other bills, including two on civil partnerships sponsored by the cabinet and the Democrat Party, were also approved in principle. The cabinet's bill was admitted in a vote of 222 to 167, while the Democrats' bill sailed through by 251 to 124 with 30 abstentions.
The third bill amending the Civil Code on civil partnerships was adopted by 230 to 169.
During the debate, Thanyawaj Kamolwongwat, an MFP list MP who is one of the most zealous supporters of the marriage equality bill, told parliament LGBTQI+ people were calling for the rights that rightly belonged to them and they deserved to be treated without discrimination in their marriages.
"The parliament would show it had a open mind if it adopted (the marriage equality bill). It would be a victory not for MFP but for the people," he said during an impassioned address in the chamber.
Issara Seriwatthanawut, a Democrat list MP who pushed for the party's civil partnership bill, argued against the cabinet's bill, saying it sought to make LGBTQI+ people second-class citizens by limiting a marriage to a union between people of the opposite sex.
The Democrats' bill, he said, is more open as it stipulates that marriage can be a union between people of any gender.
Outside the parliament, members of the LGBTQI+ rights movement submitted a letter calling on the House of Representatives to pass the marriage equality bill, saying it would make the marriage law applicable to any couple, regardless of their gender.
The letter was received by Tankhun Jitt-itsara, Secretary to the Political Working Group of the Speaker of the House of Representatives, at the parliament complex on Kiak Kai Road, Bangkok.
The LGBTQI+ group said they do not accept the government's Civil Partnership Bill, which does not fully endorse same-sex marriage, and that they are demanding equal treatment and not special treatment.
The marriage equality bill was earlier opposed by the cabinet. The government's justification was that the MFP's proposed draft was simply redundant given the government-sponsored draft bill.
On Wednesday, after the four bills made it through the first reading, the MFP hailed it as a historic move for marriage equality for people with diverse gender backgrounds and everyone in the country.
MFP leader Pita Limjaroenrat said the marriage equality bill's first reading passage marked a victorious step toward marriage equality for all.
Mr Thanyawaj thanked all sides who supported the bill and the lawmakers who saw it through its first reading adoption.
