[2] He accepted a full scholarship to study at the Germantown Academy in Fort Washington, Pennsylvania, which was provided by the sponsors of Singha Swimming Club.

[2] During his high school career, he set Germantown Academy records in the 100-yard butterfly (50.65) and 100-yard backstroke (50.40), and received all-league and all-section honors.

[7] While swimming for the Cavaliers, he received four All-American and five All-ACC honors, and eventually helped the school's team claim a 200-yard freestyle relay title at the 2002 Atlantic Coast Conference Championships.

At the age of 18, in one of the high points of his early swimming career he took a second place silver medal with a 4:30.8 in the 400-meter IM in the Southeast Asian Games in Indonesia in October 1997.

[2] Yimsomruay also competed for the national team when Thailand hosted the 1998 Asian Games, but failed to collect a medal in his signature events, the 200-meter backstroke or the 200-meter individual medley.