[3][6] Coached by Rodolphe Maréchal and Baptiste Porquet in Toulouse,[5] Siao Him Fa began appearing on the junior international level in October 2015.

In March, he qualified for the final segment at the 2018 World Junior Championships; he ranked sixteenth in the short program, nineteenth in the free skate, and seventeenth overall at the event in Sofia, Bulgaria.

[14] Dogged by injury in the fall, Siao Him Fa did not repeat his earlier success on the Junior Grand Prix, finishing off the podium at both of his events.

[18] With the COVID-19 pandemic affecting international travel, the ISU opted to assign the Grand Prix based largely on geographic location.

Siao Him Fa was scheduled to make his Grand Prix debut at the 2020 Internationaux de France, but the event was cancelled.

[21][22][23] Siao Him Fa began the Olympic season competing at the 2021 CS Lombardia Trophy, where he won the silver medal and set three new personal bests.

[24] He was then assigned to the 2021 CS Nebelhorn Trophy, winning the silver medal and qualifying a second berth for French men at the 2022 Winter Olympics.

[36][37] Disappointed not to have qualified for the Grand Prix Final, Siao Him Fa went on to win his first French national title at the championships in Rouen, beating defending champion Kévin Aymoz by a margin of over twenty points.

[38] Siao Him Fa continued his streak of success into the new year, finishing in first place in the short program at the 2023 European Championships with a new personal best of 96.53.

[48] Siao Him Fa traveled immediately to Chongqing for the 2023 Cup of China the following weekend, where he placed second in the short program behind reigning World champion Shoma Uno after falling on his quad toe loop attempt.

[49] Qualifying to the 2023–24 Grand Prix Final, Siao Him Fa doubled his planned quad Lutz in the short program, finishing sixth of six skaters in that segment and more than fifteen points back of third place.

[51] Siao Him Fa entered the 2024 European Championships in Kaunas as the favourite for the gold medal, and he won the short program despite putting a hand down on his quad Lutz and performing only a quad-double combination instead of a quad-triple.

He made errors in the free skate, but he won that segment as well and comfortably retained his European title by a margin of almost twenty points overall.

[52] He attracted notice for performing an illegal on-ice backflip at the end of his program, drawing comparisons to fellow French skater Surya Bonaly.

One program was choreographed to the ballad SOS d'un terrien en détresse from the musical Starmania, while the other one was set to a mashup of hip hop songs, "Gangsta's Paradise" and "X Gon' Give It to Ya."

[59] In late September, Siao Him Fa announced that he and his team decided that he would postpone competing until the 2024 Grand Prix de France due to an ankle injury sustained before the start of the season.

[60][61] Despite these comments, Siao Him Fa competed two weeks prior the Grand Prix de France at the 2024 CS Trophée Métropole Nice Côte d'Azur, where he won the gold medal.

[62][63] After the event, he said that there were "plenty of positives" about the competition despite the lack of time he had to prepare for it and having issues with broken boots and that he was planning adjustments to his programs.

[59] Three weeks later, Siao Him Fa competed at the 2024 Cup of China, where he placed third in the short program after falling on an attempted quadruple toe loop.

[68] The men's short program was competed the day after a mid-air plane collision occurred in the United States; many of those on board were developmental figure skaters, their parents, and their coaches.

Siao Him Fa dedicated his short program to those who died in the crash, saying, "The competition itself is no longer important compared to the message that I wanted to convey with the programme.