Thitima Noraphanpiphat was found dead on a sofa in the condo complex lobby in Bangkok’s Thon Buri area in the early hours of Tuesday morning.
A day earlier, according to footage from security cameras, the 25-year-old, who was unconscious, was seen carried into the building and later taken to the sofa by a man.
The male in question is a freelance male model, identified as Rachadech Wongtabutr who is the prime suspect in the case.
Though a doctor’s preliminary examination suggested she died of an acute heart attack, her death was described as “unnatural” by Metropolitan Police Division 8 chief Samrit Tongtao.
It remains mysterious because an initial inspection by police investigators found no trace of drug use or other foreign substances in the woman’s body.
He insisted a full autopsy is needed before officers can consider filing charges against suspects.
Part of the post-mortem, conducted by Siriraj Hospital, was revealed on Wednesday. The source said experts found “fluids” in her vagina, and also traces of injuries.
However, they have not definitively concluded the cause of her death, pending a more thorough examination, including detecting whether there are chemicals or toxins in her body and whom the fluids belong to, the source said.
Mr Rachadech was told to give a DNA sample, though a search of his room found no irregularities.
“But why did he not help her?” Pol Maj Gen Samrit said.
He also raised suspicions over the man who at first refused to allow investigators to search his room, causing the officers to force the door open.
During interrogation, Mr Rachadech claimed he and Thitima met at a party at a house in Nonthaburi’s Bang Bua Thong district.
They had some drinks, but she became quite drunk so he thought it best if he took her back to his condo.
House owner Chaiyaphon Panna told police he had hired Thitima, also known by her nickname “Bell”, for 3,000 baht to entertain guests and mix drinks on Monday.
He noticed she and Mr Rachadech became close at the party.
Mr Rachadech also admitted that when he took her to his room he changed her clothes because she had wet herself.
He denied they had sex because he was also drunk.
According to investigators, the suspect carried her to the sofa in the building’s lobby after a friend phoned him to warn that her relatives, and her boyfriend, were coming.
Mr Rachadech posted photos of the unconscious woman on his Facebook page with a message she was his “wife No.100” but later deleted them, following a barrage of criticism.