Porsoi, a native of Nakorn Sri Thammarat in southern Thailand, was made to re-enact his movements at the time of the alleged rape on a second-floor walkway in the city at the weekend.
The man claimed that the young woman was lying on the walkway and that the attack was opportunistic.
Porsio, said police, had been pointed out by a security guard as a suspect.
But the young Scots woman has been unable to identify him.
The man’s confession contradicted police reports on Tuesday, quoting the manager of the Vientiane Restaurant where the woman was refused admittance.
The manager said she was escorted to a room and the reports also quoted a neighbour, Noi Raksachon, 33, who said that if the student was being raped then she would have heard her cries.
In an interview with STV, the alleged victim said: “How come no-one in nearby houses heard anything happening? I was screaming and shouting during the attack, there’s no chance they never heard anything.
“The police have said the people living nearby just thought it was a fight and didn’t do anything.
“The police and authorities are very humiliating – their whole system has let me down, they’re making out that I was some drunken idiot and it was my fault, which was not the case”.
The woman’s mother also rounded on Thai police and cast doubt on claims that the victim was taken home.
She said: “The system there is so corrupt and if my daughter had been taken back to the flat, there was another housemate there who wasn’t aware [my daughter] was home?
“He would have heard her – instead of these ignorant people not listening to the screams of a young woman being attacked/raped.
“They go to the authorities and tell stories to make money to keep their country looking good and us Britons looking like drunken idiots.
“She does admit she was drunk but, believe me, my daughter was so happy with her new life about to begin in Thailand with a new job etc. Why would anyone make up such stories?”
Exactly what will happen next in the case was unclear last night. Police Major-General Ronnapong Saikew said the young woman was shouting at officers and had expressed her intention to leave Thailand on the next plane.
A Thai daily newspaper which published details of the victim, including her photograph, has now removed the images from the internet after protests.