Schoonbaert progressed through the youth systems of Eendracht Aalter, Zulte Waregem, and Club Brugge. In the summer of 2019, he was involved in the first-team preparations under newly appointed head coach Philippe Clement. He scored in an early pre-season friendly against KFC Heist and was included in the senior squad's training camp in Garderen.[2][3] Following this, he remained with the first team alongside fellow youth players Charles De Ketelaere, Ignace Van der Brempt, and Maxim De Cuyper.[4] Despite a promising pre-season, his performances were slightly marred by an own goal in a friendly against Deinze.[5]
In September 2019, Schoonbaert was loaned to Lommel for the season.[6] He made his debut on 26 September 2019 in a Belgian Cup match against Standard Liège, starting under head coach Stefán Gíslason.[7] He subsequently started in a league fixture against Roeselare.[8] However, the loan was terminated midway through the season, and he joined Deinze on a new loan agreement. Due to the early cancellation of the season as a result of the COVID-19 pandemic, he did not make an official appearance for the club, which was crowned champions of the Belgian First Amateur Division.[9]
In July 2020, Schoonbaert signed with Waasland-Beveren.[10] He secured a starting position in central defence under coach Nicky Hayen.[11] Despite his initial involvement, the club was relegated to the Belgian First Division B at the end of the season. The following campaign saw a decrease in playing time due to an early-season injury and a red card received during a match against Virton.[12]
The club exercised the option to extend his contract in April 2022, but by the summer, Schoonbaert was informed he was no longer part of the club's future plans.[13][14]
In July 2022, Schoonbaert signed a two-year contract with Knokke.[15] He was sent off in his first official appearance for the club during a Belgian Cup match against ASV Geel.[16]
After leaving Knokke as a free agent in 2024, he joined amateur club Zelzate in late August 2024.[17]