Yapp began playing pool at age eight.[4] An alumnus of Saint Patrick's School, he dropped out of school in 2011 to turn professional, although he eventually completed his GCE Ordinary Level examinations at Coleman College.[5] Reportedly the first professional pool player from Singapore,[5] he won the inaugural Asian Junior Pool Championship in 2014. Later that year, he became the first Singaporean to claim a world title in pool when he won the World Junior Pool Championships (Under-19) in Shanghai, China, beating Hsu Jui-an 11–10.[6] In 2021, he claimed the Singapore National Snooker Championship, defeating defending champion Peter Gilchrist 4–2.[7] In the quarter-finals of the 2021 WPA World Ten-ball Championship, Yapp defeated Jayson Shaw, which moved him up to 8th in the world rankings; he ultimately finished in third place.[8]
In the 2021 U.S. Open Pool Championship, Yapp survived a scare against Wojciech Szewczyk in the third round of the winners bracket by winning 11–10 before scoring upsets in quick succession against defending champion Joshua Filler 11–4 in the fourth round of the winners bracket and Shane Van Boening 11–5 in the Last 16. He went on to defeat both Rodrigo Geronimo and Dennis Orcollo by a scoreline of 11–6 in the quarterfinals and semifinals respectively,[9] before losing to Carlo Biado 8–13 in the final, concluding his best finish in a major tournament.[10] The following week, he won the CueSports International (CSI) Michigan 10-Ball Open, defeating Roberto Gomez 4–0, 4–2 in the final.[11] He successfully defended his Michigan Open title the following year, defeating Robbie Capito 4–2, 4–1 in the final.[12] The following month, he beat Chang Jung-Lin 7–6 in the final of the Sandcastle 9-Ball Open.[13]
In 2022, he won a bronze medal at the 2022 World Games in Birmingham, Alabama for nine-ball.
On October 18, 2024, team Asia ruled the inaugural Reyes Cup at the Ninoy Aquino Stadium in Manila, Philippines. Johann Chua, Carlo Biado, Aloysius Yapp, Duong Quoc Hoang, and Ko Pin Yi make up the team, which is coached by the tournament namesake and greatest of all time Efren Reyes.[14]
They defeated the European team with a decisive 11–6 final score. Team Europe is made up of Jayson Shaw, Eklent Kaci, Francisco Sanchez Ruiz, David Alcaide, and Mickey Krause. Yapp was named the first-ever Reyes Cup most valuable player for his outstanding performance throughout the event.[15]
A month later, Yapp successfully defended his title by winning back-to-back championships at the International Open Nine-ball in Florida. He defeated Moritz Neuhausen of Germany, 13–6, and received $40,000 in prize money.[16]
In May 2025, Yapp won his first matchroom major open title, defeating Jonas Souto Comino of Spain with a superb 13–1 in the final of the UK Open Pool Championship at Telford International Centre.[17] This significant triumph propelled him from fifth to second place in the matchroom world rankings, trailing Fedor Gorst at the top.[18] Yapp's victory has also solidified his position in the Reyes Cup rosters, securing a spot to represent Team Asia this year. In August, Yapp won the inaugural Florida Open beating Shane Van Boening in the finals and a week later he won the prestigious US Open Nine-ball Championship against defending champion Fedor Gorst and becoming the first pool player to win three consecutive World Nine-ball Tour (WNT) Open Majors (UK Open, Florida Open, US Open).
Singapore
