The winger arrived at the Gallagher Stadium in January on-loan from Premier League Crystal Palace and following his release from Selhurst Park, manager Jay Saunders was straight in with an offer.
Coker joined the Eagles at the age of 13 and was a regular in the development side prior to the loan.
He featured for Palace in last summer’s pre-season friendly and that’s where he caught the eye of the Stones boss.
Saunders told the club`s official website: “I am delighted to get Cokes on board for next season.
“I was impressed from the first time I saw him and during the loan he’s more than proved he’s got what it takes to make that step from under 23s to men’s football.
“He’s had interest from elsewhere, but it says a lot for our set-up and the fans that he wanted to agree a deal with us.”
Coker said: “I am very happy to have agreed terms. I like being here, playing in front of the fans and I want to be a part of what Jay’s planning for next season.
“We’ve spoke about what we’re trying to do next season and what he wants from me and hopefully I can fulfil that and fulfil my potential”.