However, after Rex Tso leaving his mother gym and returned to amateur boxing, his winning record decreased significantly.
Tso won the WBC Asia Continental Super Flyweight title in December 2012 in a bruising 12-round contest against Timur Shailezov of Kyrgyzstan, stopping his opponent in the 10th round.
He then captured the WBO Asia-Pacific Junior Bantamweight title against Mako Matsuyama in February 2014, winning by TKO in the 8th round of the 10-round contest.
Tso then added the WBA International Super Flyweight title to his collection after defeating Michael Enriquez in March 2015.
Tso made easy work out of the South Korean veteran, dominating the whole fight before stopping him in the fourth round.