Yimsomruay competed for Thailand in the men's 200 m individual medley at the 2000 Summer Olympics in Sydney. After winning his first gold medal at the SEA Games in Brunei, his entry time of 2:04.90 was officially accredited under a FINA B-standard. He challenged seven other swimmers in heat four, including Latvia's two-time Olympian and top favorite Valērijs Kalmikovs. He closed out the field to last place by 4.31 seconds behind winner Dean Kent of New Zealand in 2:08.38. Yimsomruay failed to advance into the semifinals, as he placed forty-third overall in the prelims.