Lamberth made 14-of-17 field goals and eight-of-nine free throws as Missouri State (16-15, 8-10) won its third-straight game.
The Bears took control of the Missouri Valley Conference game early. A Deven Mitchell jumper broker a 7-7 tie with 15 minutes left in the first half. Indiana State (14-15, 8-10) rallied to pull within a point, but Missouri State responded with a 10-0 run and took a 37-26 lead into halftime.
The Sycamores then never got closer than ten points in the second half.
Spencer Laurie and Chris Cooks both added 15 points for the Bears, who outrebounded the Sycamores 38-27.
Harry Marshall led Indiana State with 18 points, and Gabe Moore had 17 points and six assists.