Sergeant Major Sim reported to Marine Corps Recruit Depot (MCRD) San Diego, California in October 2003 for training with Company L, followed by Marine Combat Training, Camp Pendleton, California. After initial training, he transferred to Camp Johnson, North Carolina for MOS training.
In 2004, Sergeant Major Sim reported to 1st Supply Battalion, 1st Force Service Support Group, Camp Pendleton,California for duty with Supply Company. Sergeant Major Sim deployed twice to Iraq in support of Operation Iraqi Freedom.
In 2008, Sergeant Major Sim reported to Marine Security Guard (MSG) School, Quantico, Virginia. As a watchstander he served in Cairo, Egypt where he was assigned as a Squad Leader; in Dushanbe, Tajikistan; and Beijing, China; assigned as the Assistant Detachment Commander.
In 2011, Sergeant Major Sim reported to Headquarters and Service Company, Combat Logistics Regiment-15 and served as Warehouse Chief and Supply Chief. Sergeant Major Sim later deployed to Afghanistan with 1st Marine Logistics Group as the Warehouse Chief and Retrograde, Redeployment, Reset and Reconstitution Operations Element SNCOIC.
In 2013, Sergeant Major Sim reported to Headquarters and Service Battalion, MCRD San Diego, where he served as the SNCOIC for Uniform Issue and Fitting Facility.
In 2015, Sergeant Major Sim reported to Marine Corps Embassy Security Group, Quantico, Virginia, where he served as a Detachment Commander in Oslo, Norway; Instructor/Advisor at MSG School; and Company First Sergeant for Headquarters and Service Company.
In 2019, Sergeant Major Sim reported to 3d Reconnaissance Battalion and served as the Company First Sergeant for Company A and Company B. In 2022, Sergeant Major Sim reported to 9th Engineer Support Battalion and served as the Company First Sergeant for Engineer Support Company. Selected to Sergeant Major in 2022, he reported to III MEF Support Battalion in February 2023 where he currently serves as the III MEF Support Battalion Sergeant Major.
Sergeant Major Sim earned a Associates Degree in General Studies from Central Texas College, and currently pursuing a Bachelors Degree on Sports and Health Sciences from American Military University. Sergeant Major Sim's personal awards include the Navy and Marine Corps Commendation Medal with three gold stars and a Navy and Marine Corps Achievement Medal.