Thornton served as President and CEO of Planned Parenthood Association of Lubbock, Inc. (Texas) from 2003 to 2012. During that time, he was a member of the Board of Directors for the Texas Association of Planned Parenthood Affiliates (TAPPA) and served in various leadership roles including Board Chair, Treasurer, and Western Region Diversity Chair. He also served as a member of the national Cultural Diversity Steering Committee and Chair of the Annual Conference Planning Committee from 2009 to 2011. Prior to his employment with Planned Parenthood, Thornton was an accountant and Business consultant, role he continues to serve in today. Currently, Thornton serves as President of PFLAG Lubbock. His term on the Board expires June 13, 2019.