Eddie Thomason attended Eufaula High School and graduated from Midwest City High School, Midwest City, Oklahoma. He then served for eight years in the Oklahoma Army National Guard.

Undersheriff Thomason has a total of 45 years of experience in law enforcement. His experience has included patrol, communications, investigation, and administration; in the Del City and Midwest City Police Departments, the Oklahoma State Bureau of Investigation, the Oklahoma County District Attorney's Office and the Oklahoma County Sheriff's Office. He retired in 2003 as Chief Deputy at Oklahoma County. In 2005, Sheriff DeWayne Beggs selected Eddie Thomason as his Undersheriff.

Undersheriff Thomason has completed many hours of training in all aspects of Law Enforcement, up to Professional and Management levels. He is a CLEET Certified Law Enforcement Officer

Eddie and his wife have been married for forty-nine years and have three children and eight grandchildren.