Prajanchai was born as Nonthasit Phetnamthong on October 16, 1994, in Bangkok. As with so many Thai Muay Thai phenomena, his career began at a very young age—by his own account, he stepped into the ring at around five—and he grew up in a family in which, as he once put it, “almost everyone is a Muay Thai fighter.” That early start, followed by thousands of rounds of sparring and fighting, made him one of the most experienced athletes in the entire organization: by the time he arrived at ONE Championship, he had already competed in more than 400 professional bouts.
Under the guidance of the renowned PK Saenchai Muaythaigym in Bangkok—a gym he describes as “family” and as crucial to his success—Prajanchai built an impressive reputation in Thailand’s traditional stadiums. He captured multiple titles at both the prestigious Lumpinee Stadium and Rajadamnern Stadium across several weight classes, and even added a WBA Asia South featherweight boxing title.
In 2021, he moved to ONE Championship and immediately defeated established star Sam-A Gaiyanghadao by majority decision in his debut. That proved to be the beginning of an intense rivalry: in June 2023, he defeated Sam-A again, this time by knockout, to claim the interim world title, and in December 2023, he unified the title by knocking out Joseph Lasiri. In June 2024, he expanded his reign further by also capturing the ONE Strawweight kickboxing world title from Jonathan Di Bella, temporarily holding two world titles at once.
As of September 2026, Prajanchai is still the reigning ONE Strawweight Muay Thai world champion, although he lost his kickboxing title in October 2025 in a defeat to Jonathan Di Bella. His Muay Thai throne is now under serious pressure: Malaysian challenger Aliff Rakib captured the division’s interim title on July 24, 2026, at The Inner Circle 23 in Bangkok by defeating Sam-A Gaiyanghadao, becoming the first Malaysian ever to hold a ONE title and positioning himself for a unification bout against Prajanchai. That unification fight had not yet been officially confirmed as of the cutoff date, but it is widely regarded as inevitable—Prajanchai still holds the undisputed belt, but now faces a challenger who is literally at the door. He trains at PK Saenchai Muaythaigym in Bangkok, a gym he describes as a second family.
Thailand
