Thaiday was born in Sydney, New South Wales and moved to Townsville, Queensland at the age of four years.
He is of Torres Strait Islander descent.
He played junior rugby league for the Brothers club in Townsville as well as attending Kirwan State High School.
His cousin Milton Thaiday also became an NRL footballer.

Thaiday's father, Billy, was born on Yam Island in the Torres Strait and was working on Thursday Island, before becoming part of the Royal Australian Air Force (RAAF).
He signed up for RAAF, when needed the RAAF needed men and women from the Torres Strait Islands to serve in mainland Australia.
His mother, Julie Thaiday, grew up in rural Western Australia and also served in the Royal Australian Air Force.

Thaiday was questioned by police in 2009 relating to an alleged sexual assault in a Brisbane nightclub.
Thaiday was born in Sydney, New South Wales and moved to Townsville, Queensland at the age of four years. He is of Torres Strait Islander descent. He played junior rugby league for the Brothers club in Townsville as well as attending Kirwan State High School. His cousin Milton Thaiday also became an NRL footballer. 
Thaiday's father, Billy, was born on Yam Island in the Torres Strait and was working on Thursday Island, before becoming part of the Royal Australian Air Force (RAAF). He signed up for RAAF, when needed the RAAF needed men and women from the Torres Strait Islands to serve in mainland Australia. His mother, Julie Thaiday, grew up in rural Western Australia and also served in the Royal Australian Air Force.
Thaiday was questioned by police in 2009 relating to an alleged sexual assault in a Brisbane nightclub.
Sam Thaiday