Born in Lopburi, Pajonsuk began his Muay Thai education at the Lukprabart camp in Saraburi province aged six years old. As a youngster he won Thai national championships at 28, 32 and 35 kg and became a hot prospect on the local scene. Not one to be confined to just one sport, Pajonsuk also branched out into the Chinese art of Wushu, winning a gold medal in the -76 kg division at the Southeast Asian Games in Kuala Lumpur, Malaysia in 2001. He would also travel to fight, winning his first ever world title in the United States against the reigning champion and fellow countryman Matee Jedeepitak by TKO in mid-2002. Fresh from his victory in America, Pajonsuk returned to Thailand where he faced Kaolan Kaovichit, a man who had defeated him in their two previous meetings, including in a world title fight. This time Pajonsuk gained revenge by defeating Kaolan and becoming the new Lumpinee champion. Earlier that year he returned to action at the 2002 Asian Games in Busan, South Korea to pick up his second gold medal in the art of Wushu. At the end of 2003, Pajonsuk once more faced old foe Kaolan Kaovichit for the fourth and final time, losing his Lumpinee Stadium title by decision. After this defeat he travelled to Europe for a new challenge, facing Stjepan Veselic for Veslic's W.P.K.L. world title belt. Veselic had defending his title three times including an upset KO victory over Thai legend Sakmongkol Sithchuchok, but on the night in Rotterdam there was a new champion, Pajonsuk handing Vesilic a third round stoppage defeat. As he was running out of competition in Thailand where traditionally the most competitive divisions were at lower weight, Pajonsuk would fight more and more in Europe, picking up wins against the likes of Joerie Mes and Aalviar Lima and losing a close decision to Rayen Simson fighting on cards for reputable Dutch organizations such as It's Showtime and Gentlemen promotions. In 2010, he entered the EnfusionReality Show which involved some of the top Muay Thai fighters from across the world at 70 kg, with the first part of the show based at a training camp in Koh Samui, Thailand. Pajonsuk won two elimination fights in Thailand against Jan van Denderen and Shane Campbell respectively making the final 4 stage in Lisbon where he lost in the battle for the $40,000 first prize to Gago Drago via decision. By the end of 2010 Pajonsuk would make only his second appearance on a K-1 show. There had been rumors throughout the year that he would replace regular Thai K-1 MAX representative Buakaw Por. Pramuk who would not participate in the final 16 stage due to a contract dispute with the organization but in the end the relatively unknown Sagetpetch would take his place and Pajonsuk would have to make do with a super fight appearance, beating Woo Yong Choi at the event in Seoul, South Korea. Returning from a long lay off of over two years, Pajonsuk fought Michael Wakeling at Enfusion Live 3 in London, England on March 30, 2013. He lost by unanimous decision after an extra round. He lost to Tayfun Ozcan via decision at Enfusion Live 5 in Eindhoven, Netherlands on May 11, 2013.
