Herne Bay's Isthmian Premier relegation was confirmed after a 4-1 defeat at Wingate & Finchley.
It's been a difficult campaign for last season's South East play-off winners.
Victory would have kept them alive until the final day but they were well beaten.
Connor Dymond pulled a goal back after Wingate led 2-0 through Emmanuel Yeboah and Elliot Long but late goals from Long and Michael Olarewaju confirmed Bay's fate.
Josh Vincent scored the Folkestone goal in a 3-1 home defeat by Canvey Island, while Margate lost 3-0 at Billericay.
Cray Wanderers still occupy the final play-off spot after goals from Harrison Sodje and Jalen Jones in a 2-0 success against Kingstonian.
Chatham are celebrating after clinching the Isthmian South East championship at the first attempt.
Ramsgate need to win their final match at Ashford to clinch the runners-up spot after being held to a 1-1 draw by third-placed Whitehawk.
Rams, whose title hopes were effectively ended when they lost at Chatham on Easter Monday, led through Tom Carlse on the stroke of half-time.
But Rob O'Toole levelled midway through the second half, leaving the visitors a point behind Jamie Coyle's men.
Sheppey and Hythe both moved into the play-off places with a week to go.
The Ites left it late, with Brad Schafer and Warren Mfula scoring in the last two minutes for a 2-0 victory over Lancing as Jack Midson's side went fourth.
Hythe came from behind at VCD to nail a fifth successive victory and move into the top five for the first time this season.
Andrew Allassani gave the Vickers an early lead but defender Jason Fregene scored twice as the Cannons recovered to win 2-1.
Ashford suffered a third successive defeat, losing 1-0 at Chichester to Kaleem Haitham's second-half goal.
Sevenoaks can't get in the play-offs but turned on the style in a 5-2 win at Haywards Heath.
Oaks were two up inside six minutes, courtesy of Dami Olorunnisomo and a Dean Gunner own goal.
Freddie Parker scored twice and Josh Ogunseye added a late fifth.
Faversham won the battle of the relegated sides to swap places with Corinthian at the foot of the table.
Darren Phillips and Ronald Sithole were the scorers in a 2-0 away win for the Lilywhites.