James Harkins, 64, admitted targeting his victim at Whitecraigs Golf Club in Newton Mearns.
Harkins, of Lochgilphead, Argyll and Bute, was jailed for six years and four months.
The attacks began at a house in Newton Mearns where Harkins lived at the time. He told the boy it was to be their “secret”.
The boy was further attacked on a fishing trip in Stewarton, East Ayrshire as well as in a lorry that Harkins drove. The victim did not tell anyone at the time as he felt he would not be believed.
In 2012 he spoke to police in England but heard nothing back. It was only four years later when he reported his ordeal to Police Scotland that an investigation was launched.
It led detectives to another victim, who was aged between seven to 10 when she was abused.
This victim had previously reported being abused by Harkins which led to him being jailed in 1996.
But, during the fresh probe, she revealed further incidents that she had not spoken about before.
This included her being attacked at another house in Newton Mearns while she was asleep.
When the girl asked Harkins to stop he told her: “No one will believe you and they will take you away from your family.”
Harkins pled guilty to a string of charges including lewd and libidinous behaviour and attempted rape.
Commenting on the case, a NSPCC spokesman said: “Harkins’ crimes are those of predatory child abuse. With cold calculation and deliberate intent, he inflicted horrfic abuse against children, whose lives will have been devasated by his by his sickening actions.
“His victims have shown a great deal of courage, helping to ensure their abuser has again faced justice.”