Phayahong, whose real name is Jantakan Manobal, prevailed 2-1 in a split decision after four rounds against Miyuu Sugawara of Japan in the K-1: Ring of Venus event at Yoyogi National Gymnasium in Shibuya City, Tokyo on Saturday.
Despite an injury on her left knee, Phayahong emerged triumphant, winning the 2022 K-1 Women's Atomweight title.
Male Thai boxers Buakaw Banchamek, Kaew Weerasakreck, and Kongnapa Weerasakreck had earlier won the event.
Phayahong, who was born in Buriram province, is a cousin of well-known K-pop singer Lisa Blackpink or Lalisa Manobal.