There are 3 US Post Offices in Thomas County serving a total of 7,575 residents equating to 2,525 residents per post office. It's estimated that approximately 12,091 packages are handled across the 3 county post offices annually. Thomas County (standard abbreviation: TH) is a county located in the U.S. state of Kansas. As of the 2010 census, the county population was 7,900. Its county seat is Colby."