Tai Daohuang was found dead outside the apartment in Huai Khwang district on July 27. Police believe she fell from a balcony adjoined to a room on the eighth floor and do not suspect foul play.
Her mother and father, Porn Daohuang and Tantawan Chaiyawongsa, on Wednesday petitioned CIFS director-general Khunying Porntip Rojanasunan to step in and help clear up doubts over how their daughter died.
The couple were backed Ponsi Bunmichai, the first secretary of the Lao embassy in Thailand, and Suthas Ngernmuen, a lawyer and Democrat Party member.
Tai's family have raised concerns with the police after an investigation concluded that Tai jumped from the balcony of her own accord.
Royal Thai Police adviser Jarumporn Suramanee told an Aug 9 press conference that the owner of the room, identified only as Mr Amnat, had phoned Tai and asked her to come to his room that evening.
Building records show that Mr Amnat's girlfriend came to the apartment and asked a security guard to take her up to her boyfriend's room around the same time. No one answered the door, so the girlfriend persuaded the security guard to use a master set of keys to open the room.
The police investigation uncovered finger marks on the balcony, indicating Tai fell after clinging onto the balcony railings for some time.
But Tai's parents have dismissed the police findings and questioned why there were bruises around her wrist if she fell on her own. They believe the marks were caused by the grip of another person and have provided a picture of the bruises to Khunying Porntip.
The couple also say Tai had an extreme fear of heights.
Her mother told Khunying Porntip she had spoken to her daughter on the phone one week before she died. Tai had told her mum that she had received a death threat from a woman she worked with.
She said she told her daughter to quit the job and return home to Laos.
Khunying Porntip said Tai's body has been cremated and the CIFS has no authority to gain access to the police investigation files. However, she could seek intervention from the Department of Special Investigation and the National Human Rights Commission.
The only hope of finding the true cause of Tai's death now rests with witness accounts and evidence held by the police, Khunying Porntip said.