Rights activists have said that Thailand's laws and institutions still do not reflect changing social attitudes and still discriminate against lesbian, gay, bisexual and trans people and same-sex couples.

All but 11 of 380 lawmakers present in parliament's lower house voted to approve the draft legislation, paving the way to the formation of a committee to merge the four bills into one ahead of further debate and votes expected next year.

Last year, parliament debated similar draft laws and the then-government's same-sex civil union bill, but did not come to a final vote before the session ended.

The four bills debated on Thursday included one tabled by the new government that came to power after the May general election, another by civil society groups, and two by the opposition Move Forward and Democrat parties.

"In principle, this draft law is for the amendment of some provisions in the civic codes to open the way for lovers, regardless of their gender, to engage and get married," Deputy Prime Minister Somsak Thepsuthin told parliament, referring to the government's draft bill.

"This will provide rights, responsibilities and family status as equal to the marriage between a man and a woman presently in all aspects," he said.

Somsak said a government survey conducted between Oct. 31 and Nov. 14 showed 96.6% public support for the draft bill.

If the legislation is enacted and receives royal assent, Thailand would become the third country in Asia, after Taiwan and Nepal, to recognise same-sex marriage.