Siamoa rose through the ranks of A-League Men club Western United where he showed high levels of skill and promise in their academy team, where he was provided with an opportunity to represent Samoa in their 2022 OFC U-19 Championship qualification for the 2023 FIFA U-20 World Cup.
[1] In 2023, to further his chances of playing international football for Samoa, Siamoa moved to National Premier Leagues Victoria club Green Gully SC[2] On 3 July 2024, Siamoa signed with Cambodian Premier League club Life Sihanoukville as their first international signing for the 2024–25 Cambodian Premier League[3] On 14 October, Siamoa departed the club.
[4] Having impressed at National Premier Leagues level for the Western United academy team, Siamoa was called up to the Samoa U-19s.
[1] Siamoa scored twice for the Samoan U-23s during their 2023 OFC Men's Olympic Qualifying Tournament match against Tonga, in which Samoa would run out 3–0 winners.
[5][6] In 2024, Siamoa made his full international debut for Samoa when he was called up to the national team by Ryan Stewart for the 2024 OFC Men's Nations Cup[7][8] He made his debut against Tahiti on 16 June 2024.