Thanongsak Simsri (40-1, 35 KOs) charged out of the blocks with excellent body work and wasted no time in his first title defense, scoring a second-round knockout win over Sergio Mendoza (27-1, 23 KOs) at Japan's famed Korakuen Hall on Monday.

Heading back to the same country he won the belt last June after a hard-fought split decision win over Cristian Araneta, Simsri didn't box like an underdog and delivered a vicious finish to retain the IBF junior flyweight belt.

Mendoza boasted the physical advantages but didn't know what hit him.

While the Mexican southpaw caught the champion's attention with a hook in round two, the 26-year-old wasn't allowed to settle by Thailand's only current beltholder in a discipline where Southeast Asian hopefuls are often not given the respect their endeavors warrant. Performances like this quick-fire knockout help spotlight the opposite.

Simsri commanded proceedings behind his excellent southpaw jab and a pair of right hands wobbled Mendoza backwards midway through the second frame, foreshadowing a furious finish. A five-punch flurry, punctuated by a left hook crumbled the challenger against the ropes and he looked shellshocked, though more was coming.

A right hand sent him crashing down once more as he shaped to throw a counter and mercifully, referee Koji Tanaka waved it off. Simsri told The Ring's Anson Wainwright of his desire to eventually claim undisputed status at 108 pounds and will have certainly put the division on notice with a statement performance upon returning.

Among the undercard results, former IBF junior lightweight title challenger Masanori Rikiishi (17-2, 12 KOs) marked his return with aplomb, scoring a dramatic eighth-round knockout win over Lito Badenas (8-3-1, 7 KOs).