The response of a 5 lm thin silicon on insulator (SOI) 3D microdosimeter was investigated for single event upset applications by measuring the LET of different high LET ions. The charge collection characteristics of the device was performed using the Ion Beam Induced Charge collection (IBIC) technique with 3 and 5.5 MeV He2+ ions incident on the microdosimeter. The microdosimeter was irradiated with 16O, 56Fe and 124Xe ions and was able to determine the LET within 5% for most configurations apart from 124Xe. It was observed that on average, measured LET was 12% lower for 30 MeV/u 124Xe ion traversing through different thickness Kapton absorbers in comparison to Geant4 simulations. This discrepancy can be partly attributed to uncertainties in the thickness of the energy degraders and thickness of the SOI layer of the devices. The effects of overlayer thickness variation is not easy observed for ions with much lower LET as O and Fe. Based on that it is difficult to make conclusion that plasma effect is observed for 30 MeV/u 124Xe ions and further research to be carried out for ion with LET higher than 12 MeV/µm.