Vonk begin his career at RKC Waalwijk where he made 25 appearances in 3 seasons. He became first-choice goal keeper for FC Wageningen, but was forced to leave after just one season, when the club went bankrupt and ceased to exist. Vonk returned to Noord-Brabant where he played for FC Den Bosch, before joining his first club RKC, this time as their first keeper. His breakthrough came with his transfer to sc Heerenveen, a club on the rise. They reached a domestic cup final in 96/97 and finished second in the league in 99/00, resulting in Champions League football the next season. After 8 years, Vonk was approaching the autumn of his career. He left sc Heerenveen to become third-choice goalkeeper for Ajax behind Maarten Stekelenburg and Bogdan Lobonț. In a surprising turn of events, Vonk managed to play 26 games in 2 seasons. After 18 years of professional playing Vonk left the Netherlands to return to his country of birth, and played 2 seasons for Ajax' satellite club, Ajax Cape Town. He was terminated from his contract after a conflict with the coach of Ajax Cape Town, which made him a free agent. Ajax signed him due to injury problems with their current goalkeepers Maarten Stekelenburg and Dennis Gentenaar, leaving the Amsterdam club with only 1 professional goalkeeper left: Kenneth Vermeer. In the winter transfer window of '08/'09, with the regular Ajax keepers back in shape, he once again moved to an old club, sc Heerenveen to become second-choice goalkeeper behind Brian Vandenbussche. He soon took over Vandenbussche's spot and played several league games, and another cup final, which sc Heerenveen won. Continuing his tour amongst clubs he'd already played for, Vonk once again moved, this time back to his homeland South Africa, to play for Ajax Cape Town, citing family reasons, as well as sensing an opportunity to make the Bafana Bafana World Cup 2010 squad.