He was commissioned in 1991 and served with the California Army National Guard's 143rd Evacuation Hospital, US Army Reserve's 176 Med. Group and in the California Army National in the Los Alamitos Physical Examination Station. He was activated during the LA Riots, the LA Earthquake and often for medical processing of California Guardmen being deloyed for the War on Terror. He also went to Panama on a humanitarian mission (Nuevos Horizantes). MAJ Lamunyon served as Commanding Officer for Headquarters and Headquarters Detachoment, 176th Medical Group in Garden Grove, California including deployment for two major multiservice exercises. He also served as Operations Officer for the Los Alamitos Physical Examination Station and Personnel Officer (S1) for the California Medical Detachment.

In 2003, at the request of LTC Harry Glenn, MAJ Lamunyon provided predeployment combat stress consultation prior to the Geromino deployment to Afghanastan. In 2004 MAJ Lamunyon served on active duty as a case manager for the Community Based Healthcare Organization (CBHCO) providing medical case management services for California Guardsmen and Reservists returning from the War On Terror. MAJ Lamunyon consulted on the debriefing of California Guard personnel deployed for Hurricane Relief (Katrina) and served as a debriefer for those personnel. He is currently serving as the Executive Officer of the California Army National Guard Medical Detachment.