ONE Fight Night 31: Kongthoranee vs. Nong-O 2 was a combat sports event produced by ONE Championship that took place on May 3, 2025, at Lumpinee Boxing Stadium in Bangkok, Thailand. A flyweight Muay Thai rematch between Kongthoranee Sor.Sommai and former ONE Bantamweight Muay Thai World Champion Nong-O Hama headlined the event. The pairing previously to met at ONE Fight Night 28 in February 2025, which Kongthoranee won by split decision.