A prolific paedophile faces years in jail after admitting to 45 sex offences against children in the UK and abroad.
Retired English teacher Mark Frost, 70, admitted abusing nine children in Thailand between 2009 and 2012.
He pleaded guilty to 23 charges at the Old Bailey after admitting 22 charges last year.
Six of the charges relate to abuse of two pupils at a Worcestershire school during the 1980s and 1990s. Frost is due to be sentenced on Thursday.
Previously known as Andrew Tracey, Frost was brought to justice following an international investigation involving the UK's National Crime Agency (NCA), and authorities in Thailand, Spain and the Netherlands.
'Lived in fear'
Frost raped impoverished Asian boys and encouraged them to engage in sex acts after he groomed them with money, sweets, computer games and swims in his pool.
He skipped bail to avoid prosecution in Thailand but was extradited from Spain last year after his activities were uncovered by Dutch police on the computer of a man in the Netherlands.
Frost had got the boys, aged between 10 and 14, to give thumbs-up signs and make heart gestures with their hands while being filmed on a webcam engaging in sexual acts.
The court also heard details of Frost's abuse of two pupils at a school in Worcestershire during the late 1980s and 1990s.
He had sex with the boys in a school storeroom, during breaks, at his home where he lived with his adopted son, and also at a car park in Woking, Surrey, the Old Bailey heard.
One of those victims has died since coming forward, while the other said in a statement he had "lived in fear" every day following the abuse.
Frost admitted to charges that included multiple rapes, sex assaults, inciting children to engage in sexual activity and making indecent pictures.
Prosecutor Sally-Ann Hales said images and web chats seized from Frost's Dutch contact featured 15 boys, nine of whom were identified and interviewed.
The boys' mothers expressed their "sorrow" at finding out the man they regarded as a "kind and generous foreigner" had abused their children.
One of the youngsters was "too ashamed" to tell his mother and had gone from being a "bubbly, happy boy" to being "withdrawn and sometimes aggressive", the court heard.
The court heard Frost had subscribed to the now-defunct Paedophile Information Exchange (PIE), an international organisation of people who traded obscene material.
In 1986 he tried to adopt a son through the Catholic Church and was turned down, only to succeed through a local authority. The pair are now estranged.
Having joined the Scouts in 1967, he reached a senior position but resigned in 1991 before his first conviction.
He was banned from teaching by the Department for Education in 1995.
The NCA believes he may have assaulted many more youngsters he had contact with through his 25-year career in schools and as a senior Scouts volunteer.
It has appealed for any more victims to come forward who may have gone to schools where Frost taught in east London, Worcestershire and Hertfordshire.