Thomsen graduated from BYU in 1982 with a bachelor's degree in journalism. He received his master's degree in journalism from Ball State University in 1984, and his doctorate in mass communication from the University of Georgia in 1994.
Thomsen has worked as editor of corporate publications for Toyota USA and as a reporter for the Cincinnati Post. In the 2009-2010 school year some of Thomsen's students won the top paper award at the conference of the Western States Communication Association. This major accomplishment was marked by being published as the lead article in the Western Journal of Communication. Others of his papers have been published in academic journals, including the Journal of Drug Education, the Southwest Journal of Mass Communication, and more.
In 2017, Thomsen participated in Seeking spirituality in pop songs: BYU researchers identify criteria for ‘secular hymns’ and helped determine which pop songs can identify as hymns.