In December, he participated in the 1st Korea-Catalonia Youth Cup in Barcelona, Spain as a member of the South Korean national under-14 football team,[3] and was offered a contract as a result of his impressive performance.

He then played actively for Barcelona Juvenile A, and made his professional debut on 21 February, as a substitute in Segunda División B match with Atlético Levante in the 45th minute of the second half.

[13] After the end of his three-year contract with Jeonbuk and his exemption from mandatory military service as an Asian Games gold medalist, Paik was expected to return to Europe.

[15] On 4 May 2024, the final match day of the EFL Championship season, Paik scored his first goal for Birmingham in a 1–0 win over Norwich City, though the victory was not enough to save the team from relegation.

[16] Paik made his South Korea national team debut on 11 June 2019 in a friendly against Iran, as a starter.

[19] In March 2024, Paik received his first senior call-up for a year, for home-and-away 2026 World Cup qualifiers against Thailand.