No, there are no tickets to buy on site as access to Oude Schiermonnikoog strand is free and open to the public.
There is no ticket office or any form of gate at Oude Schiermonnikoog strand because access to the beach and surrounding natural areas is entirely free. It is a public natural reserve.
Visitors simply arrive at the beach and can explore it without any financial transaction on site. Any costs related to this trip are for external services, such as ferry transport to the island or bike rental, which are purchased at their respective points of service.