Kwok competed only in the men's 100 m breaststroke at the 2000 Summer Olympics in Sydney. He posted a FINA B-standard entry time of 1:05.29 from the Hong Kong Long Course Championships. He challenged seven other swimmers in heat three, including Namibia's three-time Olympian Jorg Lindemeier. He posted a lifetime best of 1:05.28 to pick up a fifth seed by three hundredths of a second (0.03) behind Lindemeier. Kwok failed to advance into the semifinals, as he placed fiftieth overall on the first day of prelims.