In 2005, Cheung entered the Miss Chinese Pageant in which she was not named as a Top 3 contestant. However, she did capture the Miss Vivacious Beauty award. She hosted What's On on Fairchild Television until April 2007 when she returned to Hong Kong as an overseas contestant in the Miss Hong Kong Pageant. Cheung wasn't a favorite to win, and was virtually ignored during the entire pageant. She was not considered even a contender to make the top 8, let alone top 5 or top 3. When she was announced as the winner, the live audience booed heavily because nobody expected her to be up there. Most of those in attendance thought that the crown should have gone to eventual runner-up Grace Wong, who had bagged the Miss Photogenic and Miss International Goodwill awards on the same night.
What followed was massive criticism totally unseen in Hong Kong pageant history. The media and the public severely bashed Cheung for being one of the least beautiful Miss Hong Kong winners ever. TVB, the organizer of the pageant, claimed that the onstage performance on the final night was just part of the game and Cheung had showed very strong communication skills when meeting the judges before the final, which might prove decisive. The public were not convinced, and insisted that Cheung's win was fixed. The bashing continued to the point that there were informal polls among internet fans on whether there should be a re-election of Miss Hong Kong 2007. Nevertheless, Cheung handled the pressure gracefully and remained calm and composed whenever she was asked about all the harsh comments made on her looks.
Cheung attended the University of British Columbia, a university that has produced beauty queens in the past. Besides Cheung, four other Vancouver contestants have won the Miss Hong Kong pageant --- Virginia Yung , Anne Heung , Sonija Kwok and Vivian Lau . The university has also produced three Miss Chinese International winners including Bernice Liu of 2001, Linda Chung of 2004, and Leanne Li of 2005.
Cheung competed in Sanya, China for the Miss World 2007 pageant in December 2007. In the pageant she made history by becoming the first Miss Hong Kong to win the Beauty With A Purpose award, based on her charity work for the "Wai Yin Association", a charitable organisation set up by a group of former Miss Hong Kong winners/participants since 1982. Cheung tied with Miss Ecuador for the award so both advanced to the semifinals automatically. She is the first Miss Hong Kong to make the semi-finals since Pauline Yeung did in 1987. The Miss World 2007 title went to Zhang Zilin of the People's Republic of China.
In January 2008, Cheung went on to compete in the Miss Chinese International 2008 pageant where she was not considered to have much chance to do well even as the host delegate. Again she broke all odds and became 1st runner up, the first Miss Hong Kong to place in the top 3 since Mandy Cho in 2004. This was again criticised as being the result of TVB's "help", especially because other contestants were mostly of very competitive quality, and Kayi's performance was considered mediocre at best.
Cheung did the worst in the relatively least competitive pageant she had entered, Miss Chinese Vancouver 2005.