Easten joined the staff of former Tulips' manager Chris Rawlinson in May 2017, and was appointed as first-team manager in September 2018.
The club currently sit ninth in the BetVictor S/East Division table.
Gay announced on social media: "It is with regret I have to inform you all that Matt Easton has resigned from his position as Manager of Spalding United.
"I would like to thank Matt for all he has done for the club. I wish him all the best for the future and he will always be welcome at Spalding United."
Keep up-to-date with our exclusive email newsletters.
Digital advertising by Minute Media
© Pitch Hero Ltd 2008-2020
Pitch Hero Ltd Registered in ENGLAND | WF3 1DR | Company Number - 636 1033