The young woman was riding during the club's motorcycle race day when she struck a wall at high speed.
Our Kelstonian family are devastated and heartbroken to learn of the death of another member of our community. The...
Posted by Kelston Boys' High School on Thursday, 11 January 2018
Hampton Downs chief operating officer Josie Spillane said the accident happened during a track day.
"Our thoughts and prayers go out to her family and friends," Spillane said.
"No one will be more deeply affected by this tragic accident than Sasha's family and friends and we are very mindful of that. We ask that you respect their privacy at this difficult time and keep them in your thoughts."
No other vehicles were involved in the accident.
"First responders were at the scene of the accident immediately and on site emergency services arrived shortly after," said Spillane.
"Sasha was airlifted to Waikato Hospital in a critical condition and her partner, who was also participating in the event, accompanied her.
"Sadly, Sasha's condition was critical and she passed away this morning."
The serious crash unit has been on site investigating the cause of the accident, and Spillane said Hampton Downs would be making no further comments until the investigations were completed.
WorkSafe is looking into whether it would investigate the incident.
"WorkSafe has been notified of the incident and is making initial inquiries to establish whether we will investigate," a spokeswoman said.
Thompson's father Rob Thompson told Fairfax that he and his wife Glennis were finding it hard to cope with their daughter's death but felt grateful for family support.
A friend has posted on social media that she was "absolutely devastated".
"One of the most gorgeous girls I know - Sasha Thompson has passed away," the friend said on Facebook.
"I cannot believe this has happened and it's going to be a very hard few weeks for everyone who knows and cares about her."
She said in the post that Thompson had recently deleted all of her social media.
"I miss you so much already and I'm so glad we caught up over Christmas, I love you," the friend wrote.
Meanwhile, staff and trustees at Kelston Boys High School where Thompson's mother Glennis works, said they too were "heartbroken".
"Our Kelstonian family are devastated and heartbroken to learn of the death of another member of our community," its Facebook post said.
"The Board of Trustees, Principal and staff send love, support and condolences to Glennis and Rob Thompson on the loss of their beautiful daughter Sasha who died in a tragic accident ... while doing what she loved so much; racing her bike at Hampton.
"Our thoughts and prayers are with you and your whanau Glennis in this heart-breaking time."
Riders' Corner, a public facebook page, posted that "the girl on the pink bike" with the Hello Kitty helmet would "be sorely missed by all".
"Many of us know Sasha and have been on rides with her, and her partner both on the track and off it," one wrote.
"She was a great person with an awesome bubbly personality and an infectious enthusiasm for riding.
"I cannot imagine what her close family and friends must be going through. But most of all her partner, who you could tell loved her dearly."
