Amnat Ruenroeng of Thailand (2nd L) celebrates his 12-round International Boxing Federation (IBF) world flyweight title fight victory against double Olympic champion flyweight Zou Shiming (R) of China at the Venetian Macao hotel in Macao, March 7, 2015. [Photo/Agencies]

Macao - Two-time Olympic gold medalist Zou Shiming lost his first title fight as IBF flyweight champion Amnat Ruenroeng of Thailand defeated the Chinese boxer by unanimous decision on Saturday.

All three judges scored the bout 116-111 for Amnat (15-0, 5 KO), who overcame being knocked down in the second round.

Zou is propelling boxing's surge in popularity in China, but he came up short in the biggest test so far, the record in his short pro career falling to 6-1 (1 KO).

Amnat landed more effective jabs than Zou, and kept him at bay with his 13-centimeter (five-inch) reach advantage, successfully defending his flyweight title for the third time.

Zou dropped Amnat with a left in round two, and when Amnat threw down Zou in the next round, the Thai champion drew boos from the audience.

Amnat received a warning for putting Zou in a head-lock on the ropes in the eighth, but his jabs were already building up a points advantage, while comfortably managing to handle whatever Zou tried.

Near the end, Zou was advised by trainer Freddie Roach to land more combinations and pick up the tempo, but Zou was frustrated from having to chase Amnat.

In the final round, Zou landed a couple of rights, but couldn't follow them up, and the final seconds were chasing Amnat amid boos from the audience.

The fight was at Cotai Arena, where Zou made his pro debut in April 2012 and won his previous six pro bouts.