At the 2000 Summer Olympics in Sydney, Phuangthong decided to drop half of his backstroke double, and experiment with the 200m butterfly. He posted FINA B-standards of 58.48 (100m backstroke) and 2:03.11 (200m butterfly) from the Southeast Asian Games in Bandar Seri Begawan, Brunei. On the second day of the Games, Phuangthong placed forty-third in the 100m backstroke. Swimming in heat two, he raced to third place in a matching entry time of 58.48, just a 1.36-second deficit behind winner Sung Min of South Korea. The following day, in the 200m butterfly, Phuangthong challenged seven other swimmers in the same heat, including 19-year-olds Zoran Lazarovski of Macedonia and Juan Pablo Valdivieso of Peru. He held off Croatia's Lovrenco Franičević to earn a fifth spot and thirty-eighth overall in 2:04.15.