Leong grew up between Macau and Zhuhai and began karting at the age of eight. His path into single-seater racing accelerated rapidly: he tested a Formula 4 car for the first time at thirteen and entered his first F4 championship with Asia Racing Team at fourteen during the 2016 F4 Chinese Championship.
His breakthrough season came in 2017 when he captured the China Formula 4 Championship title with eleven victories, securing the title with one round of the season still remaining and finishing on 345 points. He followed that immediately with the 2018 Asian Formula Renault Series championship, confirming his status as one of Asia's most promising single-seater talents.
A consistent collaborator throughout these years was engineer Josh Evans, who worked alongside Leong from the China F4 championship onwards and who later co-founded DW Evans GT, the team Leong raced with in the Lamborghini series.
Beyond his Asian titles, Leong gained experience in European competition, making appearances in the FIA Formula 3 European Championship and the FIA Formula 3 Championship at circuits including Silverstone, Monza, and Spa-Francorchamps. He also participated in Formula 3 events at the Macau Grand Prix in 2018 and 2019 before the event format changed to Formula 4 machinery for the 2020 and 2021 pandemic-affected editions.
The 2020 Macau Grand Prix was run as a Formula 4 event under Covid-19 travel restrictions, with only drivers from Macau, mainland China, Hong Kong, and Taiwan permitted to participate. Leong, driving for Theodore Smart Life Racing, won the twelve-lap race over the 6.2-kilometre Guia Circuit in a time of 00:30:11.640, becoming the first Macao driver to win his home Grand Prix since André Couto's Formula 3 victory in 2000.
Leong returned to defend his title at the 68th Macau Grand Prix in 2021, again driving for Theodore Smart Life Racing. The race was once again run to Formula 4 regulations with a restricted field drawn from Macau, mainland China, Hong Kong, and Taiwan. He retained the lead under pressure — including a close challenge from Andy Chang Wing Chung on the opening lap — and took victory to become the first Macao driver to win the Macau Grand Prix twice. The podium was completed by Chang in second and Li Si Cheng in third.
In 2024, Leong moved into GT racing, joining the Lamborghini Super Trofeo Asia with DW Evans GT. He secured two second-place finishes at the opening round at Sepang. In 2025 he returned to the series with SJM Theodore Racing with DW Evans GT, driving car number 32 alongside teammate Alex Denning.