Pajonsuk competed under his birthname of "Angkhan Chomphuphuang" in the welterweight (– 69 kg) division at the 2006 Asian Games settling for the silver medal in a lost bout against Kazakhstan's Bakhyt Sarsekbayev (8-28). He qualified for the 2008 Summer Olympics at middleweight among others knocking out Elshod Rasulov. He beat Cho Deok-Jin but was upset by Vijender Singh.