Investigating officers say Pongpatana Porsoi, a native of Nakorn Sri Thammarat in Southern Thailand, told them he assaulted the student as she lay semi-conscious outside her room after a bout of heavy drinking.
Porsoi, 26, re-enacted his movements in the lead-up to the alleged attack, which is reported to have taken place on a second floor walkway in the city in the early hours of Saturday morning. He is said to have described the incident as opportunistic.
Officers claim Porsoi was pointed out as a suspect by a local security guard before admitting the crime.
However, when the Scottish student, who is from the Highlands, was asked to identify him, she is reported to have said: "I can't tell."
The woman has admitted she remembers very little about what happened.
Officers say they will now look at forensic evidence in the case, but it is likely Porsoi will be charged with the offence.
The reported confession came as the victim's mother criticised Thai police and press for being "corrupt".
Officers previously claimed the woman had been drinking and causing a disturbance and was escorted out of a bar to the room she was renting nearby – a version of events disputed by the alleged victim.
Her mother said: "The system there is so corrupt. If my daughter had been taken back to the flat, there was another housemate there who wasn't aware she was home.
"He would have heard her ...instead of these ignorant people not listening to the screams of a young woman being attacked and 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. Why would anyone make up such stories - to make themselves out as foolish?"
In an interview earlier this week, the alleged victim also told of her disappointment at the way the case has been handled by police.
She said: "The police have said the people living nearby just thought it was a fight and didn't do anything.
"I was screaming and shouting during the attack. There's no chance they never heard anything.
"The police and authorities are very humiliating. Their whole system has let me down. They are making out that I was some drunken idiot and it was my own fault, which was not the case."
The woman also claimed to have been attacked by four men, two of whom raped her.
The Foreign Office said it was providing consular assistance to the student, who wants to return to the UK as soon as possible.
A Thai daily newspaper which published details of the victim, including her photograph, has now removed them from the internet after protests.