Thomas totaled 16 points and pulled down six rebounds. Johnson scored 15 points and Martin added 12 as the Bearkats upped their season record to 5-6.
Houston Baptist (0-15) was led by Shanice Steenholdt with 24 points and 15 rebounds.
Aggressive defense by the Bearkats limited the Huskies to 33 percent shooting (19-of-56) from the field with only one three point basket in 16 attempts. The Kats also out-rebounded HBU 52-34.
Johnson and Jasmin Wiley led Sam Houston with seven boards apiece. Wiley scored seven points. Angela Beadle scored six.
Houston Baptist held a pair of early two-point leads and trailed by only a basket, 25-23, at the 6:44 mark in the first period. A field goal by Beadle started a 12-4 for Sam Houston as the Kats took a 37-27 lead into the locker room at intermission.
SHSU came out with a hot hand early in the second period, coming out with a 10-1 run and eventually leading by as many as 22 points late in the contest. The Bearkats hit 29-of-73 for 39.7 percent shooting from the field.
The defending Southland Conference Western Division co-champions, Sam Houston will begin league action this Saturday at 2 p.m. at UTSA.