Prescott played 128 games with Richmond and Fremantle between 1993-2001, before coaching Claremont in the WAFL (2004-07), and then spending three years each with Essendon (2008-2010) and Fremantle (2011-13).
Suns football manager Marcus Ashcroft said Prescott's experience would be a huge asset.
"We are really pleased to add a person of Ashley’s experience and character to the club," Ashcroft said.
"He brings a wealth of knowledge having played and coached at the elite level for over 20 years."
Fraser joined the Suns' coaching panel after retiring as a player at the end of the 2012 season.
Ashcroft said he had impressed during his short time as coach and was well placed to take control of the reserves side.
"Josh is no stranger to our football club, he has a great understanding of what we have been trying to achieve over the last three seasons," he said.
"With the assistance of Andy Lovell (head of development) and Ashley, we are confident Josh is the ideal person to coach our NEAFL team."
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