Jonker attended the Rijksakademie van beeldende kunsten in Amsterdam, where he studied under, among others, Piet Esser. He worked as a figurative sculptor. One of his works is the seven and a half kilogram sculpture for the Ard Schenk Award, which has been awarded since 1990 by the KNSB to the 'Skater of the Year'. He used an action photo of Ard Schenk for his design. In 1957, Jonker founded the Boetseergroep De Orchidee in Haarlem. He was also a member of Kunst Zij Ons Doel, the Haarlem professional association of visual artists.