The bout in question was the second meeting between Amnat Ruenroeng (17-1, 5) [อำนาจ รื่นเริง] and Filipino Johnriel Casimero (22-3, 14), a rematch that came after last year's farcical and foul filled bout in Amnat's native Thailand.
The bout started much like their first. From the opening bell it seemed like Amnat was sharper, stronger, faster and and physically the better fighter. He seemed able to box when he wanted and wrestle when he wanted, almost trying to bully the Filipino mentally, and in fact seemed to stiffen the Filipino part way through the round. The second followed a similar pattern with the Filipino being made to look second best to the defending the champion.
In round 3 Amnat sent Casimero to the canvas, though rightfully it was ruled a push with Amnat scarcely hiding his dirty tactics and dark arts.
Surprisingly the bout flipped on it's head in round 4 when Casimero landed a sweet counter up top that sent Amnat down. The shot would have dropped anyone in the division and Amnart unsurprisingly dropped hard, though amazingly got back to his feet. Although he got up he never seemed to recover and Casimero went on the hunt, smelling blood. Several waves of the Casimero storm were thwarted, with Amnat blocking, holding and spoiling his way through some of the round but a left hand to the body put the Thai down for the count.
With the win Casimero becomes a 2-weight world champion, having previously been the IBF Light Flyweight champion, and leaves the Flyweight picture looking extremely exciting, with him, Roman Gonzalez, Juan Francisco Estrada and Kazuto Ioka all holding titles. As for Amnat this could be the end, unless he fancies a trilogy with Casimero, he's getting on in terms of age and after a stoppage loss like this he may find it very hard to get notable opponents to face him and his dark arts style.