BANGKOK (Reuters) - Thai lesbian couple Vorawan "Beaut" Ramwan and Anticha "An" Sangchai are patiently waiting for the passage of their country's same-sex marriage law so that they can cement their relationship after four years together.

"Once the law comes into effect, we will sign our marriage license," said Anticha, a university lecturer. "We've been waiting for this for a long time."

The marriage equality bill is expected to pass through its final reading in Thailand's upper house of parliament on Tuesday, said Wallop Tangkananuruk, chairman of the senate committee for the bill.

It will then be sent to the king for approval and come into force 120 days after being published in the Royal Gazette, making Thailand the third territory in Asia after Taiwan and Nepal to legalise same-sex marriage.

The Southeast Asian nation, known for its vibrant cultural scene and tolerance, has long been a popular destination for LGBTQ+ travellers.

Thousands of LGBTQ+ revellers and activists gathered for a parade through the streets of Bangkok this month, joined by Thai Prime Minister Srettha Thavisin, who came dressed in a rainbow shirt to celebrate Pride Month.

For Anticha and Vorawan, marriage equality represents more than a ceremony. It is a marker that their relationship is recognised and granted the same legal protections as heterosexual couples, they said.

"The passage of this law is a (social) movement, pushing the boundaries by acknowledging our existence, " Anticha said.

The law also formalises their ability to look after one another legally, said Vorawan.

"It would give us a more sense of security for our lives," said the 32-year-old nurse. "It's something that we've never had before."

(Additional reporting by Panarat Thepgumpanat; Writing by Chayut Setboonsarng, Edited by Devjyot Ghoshal and Gerry Doyle)

By Artorn Pookasook and Juarawee Kittisilpa