Hapkidoist Bong Soo Han, who began studying his art as a youngster in Korea, served as Laughlin's double in some of the karate sequences in the movie Billy Jack. Although the on location filming took six weeks, Han and Laughlin spent months working out each sequence.

Billy Jack was said to be among the most important movies of 1971. It's realistic, well-executed hapkido scenes enjoyed unusually long engagements in a number of large cities. At the time Laughlin approached Han, he operated a school at which he taught his art to 70 students. Laughlin has continued to study and practice hapkido.