try for Souths in their 36–18 win at McDonald Jones Stadium. During the 2018 All-Stars match at AAMI Park, Melbourne, Gagai was eligible to play for both representative teams as he had Torres Strait Island and Maori heritage. Gagai was then selected to the Maori All-Stars Team. 2019 Before the 2019 NRL season started Gagai chose to play for New Zealand Maori kiwis against the Indigenous Australian All Stars and in that game he scored two tries. In Game 1 of the 2019 State of Origin series, Gagai scored 2 tries and won man of the match in Queensland's 18–14 victory at Suncorp Stadium. After the match, Gagai finished with 256 run metres, two linebreaks, three tackle breaks and 11 tackles. In round 19 against St. George, Gagai scored two tries as South Sydney won the match 20-16 after the final siren had sounded. Gagai finished the 2019 NRL season playing 25 games and scoring 10 tries. He played in the club's preliminary final defeat against the Canberra Raiders as the club fell short of a grand final appearance for the second year in a row. 2020 In round 5 of the 2020 NRL season, Gagai scored two tries as South Sydney defeated the Gold Coast 32–12 at Bankwest Stadium. In round 8, Gagai scored the match winning try for Souths as they defeated Canterbury 26–10 at Bankwest Stadium. In round 9, Gagai scored his first NRL hat trick as Souths defeated the West Tigers 18–10 at Bankwest Stadium. In round 18 against Wests Tigers, Gagai scored a try but was later sent to the sin bin after throwing the ball at Wests player Luke Brooks. Brooks retaliated punching Gagai in the face before the pair traded punches sparking an all in brawl. Souths would go on to win the match 26–24. Gagai finished the season with 19 appearances and 11 tries. He played in the club's preliminary final defeat against Penrith as Souths fell at that stage in the competition for a third year in a row. 2021 In round 12 of the 2021 NRL season, Gagai scored a hat-trick in South Sydney's 38-20 victory over Parramatta. On 9 August, it was announced that Gagai had signed a three-year deal to rejoin Newcastle in 2022. In round 24, Gagai was sent to the sin bin during South Sydney's 52-12 victory over arch-rivals the Sydney Roosters. Gagai played a total