Thomas was the pianist head of an important Texas blues clan which included his daughter Hociel Thomas, his siblings Beulah ‘Sippie’ Wallace and Hersal Thomas, plus Bernice Edwards, not a blood relative, but raised with the family. Thomas was an important composer (of New Orleans Hop Scop Blues and Muscle Shoals Blues among other tunes), and a publisher, for a time in partnership with Clarence Williams.
Williams attributed the origin of the boogie woogie piano style to Thomas. Thomas was certainly among its earliest important exponents. "New Orleans Hop Scop Blues", published in 1916, is claimed to be the first twelve-bar blues to be written with a boogie-woogie bass line. With brother Hersal, he also copyrighted "The Fives" in 1921, a classic later performed by many pianists.
On disc records, he made "The Rocks" in 1923 (credited as Clay Custer), a solo which contains the earliest recording of a walking bass, accompanied Sippie's friend Tiny Franklin, and made one record under his own name, and a few with his jazz group, the Muscle Shoals Devils.