Thomas was elected Commonwealth attorney for the seventh judicial district of Kentucky in 1903 for a term of six years.
Thomas was elected as a Democrat to the Sixty-first and to the eight succeeding Congresses and served from March 4, 1909, until his death at Red Boiling Springs, Tennessee, September 3, 1925. During his time in Congress he introduced a bill in 1915 and 1920 to allow Civil War veterans of Kentucky that served over 90 days in the Kentucky State Militia to receive pensions. This bill was denied.
He was interred in Evergreen Cemetery, Greenville, Kentucky.