Thanongsak Simsri

Thanongsak Simsri (, born 17 June 2000), also known by his ring name Petchkoson Greentsuda (เพชรโกศล กรีนสึดะ) is a Thai professional boxer who has held the International Boxing Federation (IBF) light-flyweight title since June 2025. He is Thailand's 50th world boxing champion and the third to hold this weight class title in this organization, following Muangchai Kittikasem in 1989 and Saman Sorjaturong in 1995.

Professional career Early career Simsri made his debut on 20 June 2018 against fellow debutant Thanapong Saekoo in Samut Prakan, Simsri won via first-round TKO.

Simsri was scheduled against the reigning WBA and The Ring light-flyweight world champion Hiroto Kyoguchi for Kyoguchi's third title defense on 3 November 2020, Simsri was at the time the eleventh-ranked contender in the WBA light-flyweight rankings. On 2 November 2020, one day before the fight, Kyoguchi announced he was unable to fight, as both he and his coaches had contracted COVID-19.

Simsri vs. Yabuki After composing a record of 24–0, on 10 September 2022, Simsri fought former WBC light-flyweight world champion Masamichi Yabuki in what was promoted as a world title prelude for Yabuki, the fight was scheduled for a catchweight of 50 kilograms. Simsri lost the bout via seventh-round technical knockout, Yabuki knocked his opponent down twice prior to the stoppage, in the second and sixth rounds.

OPBF light-flyweight champion Simsri vs. Fajardo On 13 April 2024, Simsri challenged the knockout-artist and reigning OPBF light-flyweight champion Miel Fajardo for Fajardo's first title defense, the bout was held in Edion Arena, Osaka, Japan, Simsri prevailed via unanimous decision, thereby becoming the new OPBF champion, Simsri was down once in the tenth round prior to the decision-announcing.

Simsri vs. Taniguchi On 15 December 2024, Simsri made his third title defense against former WBO mini-flyweight world champion Masataka Taniguchi in Sumiyoshi Sports Center, Osaka, Simsri successfully defended the title via split decision. On 26 April 2025, it was confirmed that their bout was finalized and will take place on 19 June 2025 at the Ota City General Gymnasium in Tokyo, Japan. Simsri defeated Araneta via split decision to become new IBF light-flyweight world champion, Simsri was in control of the early stages but was dropped in the third-round by a counter left hand, Simsri stood up and quickly adjusted, and later controlled most of the bout to win decisively.

After winning the world championship, Simsri dedicated the title to his grandmother, who had died just two days earlier, shortly after he had celebrated his 25th birthday.

Simsri vs. Mendoza On April 13, 2026 (Songkran Day in Thailand), at Korakuen Hall in Tokyo, he made his first title defense by defeating the 26-year-old world No. 1 contender Sergio "Yoreme" Mendoza of Mexico via TKO (referee stoppage) in the second round, after Mendoza had previously been knocked down and given an eight-count. The victory ended Mendoza's winning streak at just 26 fights, with the bout concluding much more quickly than expected.

Personal life Although Simsri fights under the Japanese promoter Green Tsuda, which is based in Osaka, he lives and primarily trains in Thailand. He only travels to Japan when a fight is scheduled.

Professional boxing record