BANGKOK, Thailand (AP) _ Unbeaten Saen Sor Ploenchit of Thailand retained the WBA flyweight title with a unanimous 12-round decision over previously undefeated Chang Young-soon of South Korea Sunday night.

Saen, scoring his 23rd victory, wore down Chang with left jabs to the head, knocking him down in the ninth and 12th rounds.

Chang, bleeding from the nose for most of the fight, charged back each time with a flurry of punches to the champion's midsection and head. But his exhaustion showed in the final round when he collapsed on top of Saen and into the ropes.

The judges awarded the fight to Saen by scores of 117-113, 116-113 and 119-111.

The loss was Chang's first in 17 fights. He has won 13 by knockouts.

Saen has five knockouts, including two in seven championship bouts.

Each fighter weighed 112 pounds.