Ongjunta represented Thailand at the 2015 Southeast Asian Games, held in June 2015, once again competing in the bantamweight division.

[2] Ongjunta competed in the flyweight event of the 2017 Southeast Asian Games, held in August 2017 at the Malaysia International Trade and Exhibition Centre MITEC.

Although he was able to win his first two fights, against Syed Muhammad Asif and Murtadha Al Sudani by unanimous decision, he eventually lost to Kharkhuu Enkhamar in the tournament quarterfinals.

He secured Thailand's fourth gold medal, after beating Subaru Murata, Chingiz Natyrov and Malik Nahim by unanimous decision.

Ongjunta was scheduled to fight Adrian Lerasan for the vacant WBA super-flyweight title on 1 March 2020, in his fifth professional bout.

[8] After beating Pakphum Tawinram by a first-round technical knockout in a super-flyweight bout on 28 November 2020 and Khachonsak Pothong by a third-round technical knockout in a bantamweight bout on 19 December 2020,[9] Ongjunta moved down to flyweight to face Suriyan Satorn for the vacant WBA Asia flyweight title on 27 March 2021.