Additionally, he competed for the Singapore-based organization ONE Championship in their all-striking ONE Super Series format, where he has fought in both Muay Thai and kickboxing.

On March 25, 2011, Phetmorakot defeated Wanchai Sor Kittisak to win the Lumpinee Stadium Mini Flyweight (105 lbs) title.

On April 9, 2013, he defeated Thong Puideenaidee at Lumpinee Stadium to win the Thailand (PAT) Super Bantamweight (122 lbs) title.

He successfully defended his Lumpinee Stadium title a third time by defeating Genji Umeno via unanimous decision in Japan on April 19, 2015.

On December 25, 2015, Phetmorakot defeated future Glory Featherweight Champion Petpanomrung Kiatmuu9 to win the Toyota Vigo Marathon 62 kg Tournament.

[3] On October 4, 2019 at the Hilux Revo Muay Thai Marathon in Chiang Rai, Phetmorakot defeated Ali Ebrahimi by second-round KO to win the WBC Muaythai Diamond Middleweight Championship.

[9] Phetmorakot was later selected as a competitor in the ONE Super Series Kickboxing Featherweight World Grand Prix, which included other fighters like Yodsanklai Fairtex and Giorgio Petrosyan.

On May 17, 2019, Phetmorakot faced Giorgio Petrosyan in the Kickboxing Featherweight World Grand Prix Quarter-Finals at ONE Championship: Enter the Dragon, where he won a closely contested split decision.

[11] A rematch was scheduled for July 12, 2019 at ONE Championship: Masters of Destiny, where Phetmorakot lost by unanimous decision and was eliminated from the Kickboxing Featherweight World Grand Prix.