Sonsona started boxing at seven years of age under the tutelage of his uncle. Before fighting as a professional, he fought 150 times as an amateur.
He won his professional debut on points then knocked out his next ten opponents in short rounds. All his first opponents were unknowns but then he also knocked out former two time WBC world Champion Thai fighter Wandee Singwancha (record 57-10) via second-round KO.
Sonsona climbed up in weight to challenge José López for the WBO super flyweight title on September 5, 2009. He scored a knockdown in the fourth round and fought his way to a unanimous decision victory.
On November 20, 2009, Sonsona vacated his newly won WBO super flyweight title after not being able to make the weight limit for his first title defense. The bout still went on with the WBO title at stake but only his challenger, Alejandro Mutchuneli (22-7-1), had the chance to win. At the end of the bout, the judges had it a split decision. With the result, Sonsona set a record for the Philippine boxer who had the shortest reign as world champion: 2 months and 17 days.
On February 27, 2010, Sonsona jumped two weight divisions, challenging undefeated Wilfredo Vázquez, Jr. for the vacant WBO super-bantamweight title. Vázquez, son of former world champion Wilfredo Vázquez, defeated Sonsona by knockout in the fourth round.