He then carried him to bed under the guise of putting him down to sleep.
The boy woke with Davis lying behind him with his hand down his pants.
In relation to the representative drug charges, he supplied the boy with cannabis on 200 occasions and oxycodone on 10 occasions.
Judge Michael Crosbie said Davis' sexual offending "contained a dimension of grooming".
It was "negative, predatory and destructive" offending, he said.
Davis originally claimed the boy had fabricated the story to get ACC cash.
Despite the man's recent concessions in front of the Parole Board he was declined early release.
"He recognised that he had not as yet received any treatment for his offending and that the psychological assessment that had recently been carried out recommended that he undertake the Kia Marama Programme [sex-offender treatment]. He is motivated to do so," board convener Martha Coleman said.
Ms Saunderson-Warner said her client's mental health issues and his problems concerning a past head injury may make him unsuitable for the programme.
Davis' security classification was minimum and the board heard he had completed programmes in prison, including in literacy and numeracy and courses in carpentry and joinery.
His release date is June 2021 and he will appear again before the Parole Board in a year.