Twenty-five-year-old Wassmer was part of the Margate team which won promotion in 2015.
He started his career at Hayes & Yeading United, working his way through the youth system, breaking into their first-team when they were a National League side.
His performances caught the eye of Steve Evans at Crawley Town and Wassmer joined the Sussex club as they moved into the Football League.
After two seasons at Crawley he returned to non-League football, initially on loan at Fleetwood Town and then permanently at Cambridge United.
A spell back at Hayes & Yeading United followed before he moved to the Kent coast.
The Magpies can also confirm that Ryan Peters, Christian Smith and Kieron Forbes have committed themselves for next season.