The Aztecs won their 10th straight game since dropping their season opener by nine points to Arizona, currently the top-ranked team in the country.
San Diego State handily outshot and outrebounded the Rams, but allowed Colorado State to stay within striking distance by making only 12-of-21 from the foul line.
Thames hit 8-of-14 from the field and was one of only two San Diego State players to reach double figures. Winston Shepard scored 17 for the Aztecs.
Colorado State (9-5, 0-1 MWC) was led by Daniel Bejarano with 22 points and eight rebounds.