Rex Tso Sing-yu was born on 15 July 1987 and grew up in Tuen Mun, Hong Kong; a super flyweight professional boxer nicknamed the Wonder Kid, he stands about 1.7 metres and fights southpaw. He won his professional debut in Hong Kong on 22 September 2011 and went on to compile an unbeaten run of 22 fights, becoming Hong Kong's first undefeated professional boxer. By 2014 he was ranked fifth in the world at super flyweight by the World Boxing Organization and fought on a Top Rank card in Macao as WBO Asia Pacific champion. At the end of 2016 he rose to world number one in the WBO super flyweight rankings, and in November 2017 he beat Japan's Kohei Kono for his 22nd win, the bout having been interrupted when the two clashed heads and he was cut near the left eye. He held the WBO Asia Pacific, WBC Asian Continental and WBO International super flyweight titles. In 2018, after defeating Taipei's Chiang Yi-hung, he announced his retirement from the professional ring to compete as an amateur with the aim of qualifying for the Olympics. In January 2020 he founded the boxing gym RCT Hong Kong, turning his focus to training younger fighters, and on 24 August 2025, almost eight years after his last pro bout, he returned in Manila, stopping the Filipino Vergilio Silvano in the fifth round to move his record to 23 wins and no losses and signing a contract for three professional fights in a year.
Rex Tso is the face of professional boxing in Hong Kong, bringing a niche sport into the mainstream. His 22-fight unbeaten run and world number one ranking showed that a Hong Kong boxer could stand on the international stage; after retiring he opened a gym to train newcomers and, at 37, returned in 2025 to pursue the world title that still eludes him.
Achievements
- 2011 · Won his professional boxing debut in Hong Kong.
- 2016 · Became world number one in the WBO super flyweight rankings.
- 2017 · Defeated Japan's Kohei Kono for his 22nd win, keeping his record unbeaten.
- 2025 · On his comeback after eight years he stopped the Filipino Vergilio Silvano in the fifth round to move his record to 23-0.