Hezekiah Thomas was born on August 14, 1837, in Ohio to Camm and Rachel Thomas. His father was a farmer who owned $7,000 of real estate and $900 of personal property by 1860. Thomas grew up and attended school in Somerset, Ohio.
He enlisted in the Union army in June 1861, and he mustered in as a private in Company A of the 25th Ohio Infantry on June 12. He was promoted to sergeant soon afterward. He was wounded in the Battle of the Camp Alleghany in December 1861, but he eventually recovered and rejoined the regiment. The regiment took part in the Second Battle of Bull Run, the Battle of Chancellorsville, and the Battle of Gettysburg. He was promoted to 1st lieutenant on August 11, 1864, and he mustered out on June 18, 1866.
Thomas returned to Somerset after the war, and by 1870, he was working as a teacher. He married Eliza Jane Lee on November 7, 1872, and they had three children: Lotta, born around 1874; Mattie, born around 1879; and Hattie, born around 1879. They lived in Jerusalem, Ohio, until the late 1800s, when they moved to Malaga, Ohio. He died of liver cancer in Barnesville, Ohio, on October 25, 1909.