A young Saudi woman who caused an international sensation as she sought asylum abroad arrived in Toronto today where she was welcomed with open arms.

Foreign Minister Chrystia Freeland greeted Rahaf Mohammed al-Qunun, 18, after she landed in Toronto.

She posed for photographers with Ms Freeland at her side, but made no statement.

"She had a pretty long journey and is exhausted and prefers not to take questions for the moment," Ms Freeland said.

"Canada has been unequivocal that we'll stand up for human rights and women's rights around the world," Prime Minister Justin Trudeau said earlier in the week.

"When the United Nations made a request of us that we grant al-Qunun's asylum, we accepted."

The move is sure to further strain Canada's relations with the kingdom that went sideways last August over Ottawa's rights criticism of Saudi Arabia, prompting Riyadh to expel the Canadian ambassador and sever all trade and investment ties in protest.

Canada also sparked fury in Riyadh by demanding the "immediate release" of jailed rights campaigners, including Samar Badawi, the sister of jailed blogger Raif Badawi, whose family lives in Quebec.

Ms Qunun's attempt to flee the ultra-conservative kingdom was embraced by rights groups as a beacon of defiance against repression.

Thai authorities initially threatened to deport her after she arrived in Bangkok from Kuwait last weekend.

But armed with a smartphone and hastily opened Twitter account, she forced a U-turn from Thai immigration police who handed her into the care of the UN's refugee agency as the #SaveRahaf hashtag bounced across the world.

"Ms al-Qunun's plight has captured the world's attention over the past few days, providing a glimpse into the precarious situation of millions of refugees worldwide," UN High Commissioner for Refugees Filippo Grandi said.

"Refugee protection today is often under threat and cannot always be assured, but in this instance international refugee law and overriding values of humanity have prevailed."

Raif Badawi's wife Ensaf Haidar also praised Canada, calling Foreign Minister Chrystia Freeland on Twitter "the real hero" behind efforts to prevent Ms Qunun's repatriation to Saudi Arabia.

Ms Qunun alleged that she was abused by her family - who deny the allegations - and rights groups also said she had renounced Islam, risking prosecution in Saudi Arabia.

Ms Qunun first said she was aiming for Australia where officials had suggested they would give serious consideration to her claim for asylum, which was endorsed as legitimate by the UNHCR on Wednesday.

But last night, Thailand's immigration police chief Surachate Hakparn said a smiling and cheerful Rahaf was bound for Toronto and had left on a flight.

"She chose Canada... Canada said it will accept her," he told reporters at Bangkok's main airport.

"She is safe now and has good physical and mental health. She is happy."

Ms Qunun left from the same airport where her quest for asylum began less than a week ago in a swift-moving process that defied most norms.

Yesterday afternoon Ms Qunun posted a cryptic tweet on her profile saying "I have some good news and some bad news" - shortly afterward, her account was deactivated in response to death threats she had faced, her friends said.

But she was back online later in the day, tweeting: "I would like to thank you people for supporting me and saving my life. Truly I have never dreamed of this love and support."

Ms Qunun's swift use of Twitter saw her amass more than tens of thousands of followers within a week, highlighting her plight at a time when Saudi Arabia's human rights record is under heavy scrutiny following the murder of journalist Jamal Khashoggi last year.

Her deployment of social media allowed her to avoid the fate of countless other refugees who are quietly sent back home or languish in Bangkok detention centres.

Ms Qunun refused to meet her father and brother, who arrived in Bangkok to try take her back to Saudi Arabia.

Mr Surachate said her father and brother were due to return home on a flight today.