Thomas represented the Los Angeles Figure Skating Club from 1983 on. She was coached by Alex McGowan from age 10 until she retired from amateur competition at age 21.
Thomas won both the 1986 U.S. and World championships, making her the first female athlete to win those titles while attending college full time since Tenley Albright in the 1950s. In 1987, Thomas placed second at the U.S. Championships to Jill Trenary but rebounded at the World Championships, finishing a close second to East German Katarina Witt.
In January 1988, Thomas reclaimed the U.S. title. At the 1988 Winter Olympics in Calgary, she and Witt engaged in a rivalry dubbed the "Battle of the Carmens," as both women skated their long programs to the music of Bizet's opera Carmen
. Thomas earned the bronze medal behind Witt and Canadian Elizabeth Manley and went on to win the bronze at the 1988 World Championships.
After her figure skating career, Thomas went back to school to become an orthopedic surgeon.