Ian Ogilvie, 50, and Allan Donnelly,47, preyed on the teenager for months – even filming their sick antics.
Ogilvie was already on the sex offenders list for life at the time – and was also the subject of a supposedly strict order banning him from going near under-16s.
The pair were snared after a man allegedly asked to take part in the rape of the child alerted police.
The shocking tale emerged as Ogilvie and Donnelly admitted to a string of sex charges when they appeared at the High Court in Glasgow.
A judge said both took part in a “deeply horrifying level of depravity” - and each could face life sentences when they return to the dock later this year.
The young victim had moved to Scotland around six years ago from her home in Thailand.
She joined her mother who had earlier gone to stay with Donnelly after meeting him while he was on holiday in the Far East.
Donnelly – who had a previous conviction for lewd and libidinous conduct from the early 1980’s – developed a sick fascination with the schoolgirl.
He started having sex with the youngster when she was 15 at his home in Airdrie, Lanarkshire – while her mum was out.
Last June, Donnelly then introduced the teenager to Ogilvie – who was already on the sex offenders register for life.
Ogilvie was jailed in Northampton in 2005 after being caught with a hoard of child porn.
He and Donnelly soon abused the vulnerable youngster together often at Ogilvie’s home in Motherwell, Lanarkshire.
It was alleged the pair, earlier this year, tried to organise the rape of the girl while she was drugged.
Eric Cunningham was one of the men said to have been contacted to take part in the sick sex attack.
It was a concerned Mr Cunningham who then got in touch with police in March this year leading to Oglvie and Donnelly being caught.
Officers swooped after Donnelly was seen with the girl going to Ogilvie’s home.
She later revealed her ordeal before Ogilvie and Donnelly were charged.
Officers also seized recordings of the girl being abused – which included her being blind-folded and tied-up with a rope.
Prosecutor David Nicholson described the scenes as “very graphic footage”.
Ogilvie was later quizzed by police and recalled he had previously met Donnelly in a pub before later being introduced to the girl.
Donnelly mostly gave no comment during his interview.
The court heard the girl and her mum left Scotland soon after the arrests and have not returned.
One source close to the case said: “The girl loved it here and had made so many friends.
“It is so sad that she feels she has to leave all that behind to get away from everything that happened.
“She was just a sexual plaything to Ogilvie and Donnelly and it will take a long time for her to recover.”
The pair both admitted to having sex with a child and making indecent images while Donnelly also pled guilty to charges of sexual assault and taking her to Ogilvie’s home for him to abuse her.
Judge Lord Pentland called for a risk assessment to be carried out on the pair before sentencing in October.
This could lead to both being made the subject of an Order for Lifelong Restriction meaning they will be monitored by the authorities until each dies.
Lord Pentland said the offences were of “some gravity” adding: “They involve a deeply horrifying level of depravity.”