Judo star Stephanie Inglis suffered severe head injuries when her skirt caught in a wheel and pulled her off the bike as she made her way to the school where she has been teaching English to underprivileged children for the last four months.
The 27-year-old, who won silver at Glasgow 2014, is now being treated in a hospital intensive care unit in Hanoi, where she is in a coma.
Her parents have flown from their home in Inverness to be at her bedside.
An online fundraising campaign launched to help pay for her medical costs has now raised more than £100,000.
Her sister Stacey said: “She’s in a very critical state, she’s in a coma.
“There is a lot of bleeding to the brain and swelling, and we are just not sure what is going to happen.”
She added: “She is my big sister – I look up to her so much. She’s one of the nicest people, the best sister you could probably have.
“She’s so supportive to me, to my mum and my dad. She’s got the best advice ever, not that I always take it.
“I just want her home, I just want her home.”
She described the support the family are receiving as “amazing”.
Fellow judo athlete Khalid Gehlan created the GoFundMe page after a problem emerged with travel insurance in covering the medical bills.
He said: “We set up the fund initially just to get some money together in the hope that some people would come together and give some money towards the cost to help Stephanie.
“But I didn’t expect to get the response that we did and it’s overwhelming, but it’s testament to the kind of person Stephanie is.”
Writing on the fundraising page, he said Stephanie was being taxied on a motorbike to the school when the accident happened.
“Somewhere along this journey her dress was caught in the wheel and she was dragged off from her seat at high speeds and received severe injuries to her brain.
“If anyone can pull through this it’s Stephanie. She has been a fighter her whole life, following in her father’s footsteps and becoming an international athlete, competing for Great Britain all over the world, beating adversity, competing and winning a silver medal in Glasgow 2014 Commonwealth Games, fighting for her country and her dreams.
“Now she is fighting for her life.”