Udomchoke made his debut in the main draw of a Grand Slam in 2004 when he qualified for the US Open. He lost to Spaniard Tommy Robredo in straight sets. One of Udomchoke's highest profile matches was his 2006 Australian Open 1st round match against No. 3 seed David Nalbandian. After starting out slowly, Udomchoke shocked Nalbandian by winning the third and fourth sets. However, his energy soon wore down, and despite pushing the World No. 3 to five sets, Udomchoke lost 2–6, 2–6, 6–1, 7–6, 1–6. In the 2007 Australian Open, Udomchoke advanced to the third round, losing to 14th-seeded Novak Djoković after defeating 24th-seeded Juan Carlos Ferrero. Udomchoke qualified for Wimbledon in 2007 and was defeated in the second round by Andy Roddick, though put up an extremely good fight and lost in a tie-break at the end in a final score 6–3, 6–4, 7–6.