The undefeated Thai boxed at distance after surviving a second round knockdown to claim a 116-111 verdict on all three judges’ scorecards as Zou struggled to land many clean punches.
It was a crushing defeat on home soil for China’s double Olympic gold medallist Zou, who was fighting for the world title in just his seventh professional contest and only his second over the full distance of 12 rounds.
After a cagey opening, the fight briefly burst into life in the second round when Amnat went down after the first real flurry of punches thrown by Zou.
It looked liked the Thai had slipped over but the referee gave him a standing count.
Both boxers struggled to land clean shots in the opening half of the fight as they seemed content only to box from distance and grab and hold on once in close.
But it was Amnat, who improved his unbeaten record to 15 wins, who was able to prevent Zou from landing any flurries and counter with occasional stinging ripostes of his own.
Zou, despite having Manny Pacquiao’s fabled trainer Freddie Roach in his corner, appeared to lack the craft to cut off the ring and trap the Thai, and never really threatened to hurt his opponent.
China has only once before had a world champion outside of the amateur ring, and that was at the little recognised World Boxing Council “minimum weight” (light flyweight) category which Xiong Zhaozhong won in 2012 and defended twice.