Radiation monitoring in space radiation is complex due to Galactic Cosmic Rays (GCR), Solar Particle Events (SPE) and albedo particles. Thermal neutrons are an important component in the Moon radiation albedo field which can cause single event upset (SEU) in electronics when they interact with the 10B present in electronic components. In this work, we studied an application of silicon on insulator (SOI) microdosimeters for neutron monitoring in various mixed radiation field environments. A 10 μm SOI microdosimeter was utilized in conjunction with a 10B4C thin film converter to successfully measure the thermal neutron contribution out of field of a therapeutic proton beam as well as an 18 MV X-ray LINAC. The microdosimeter was placed downstream of the Bragg peak (BP) as well as laterally out of field of the proton beam and at two positions along the treatment couch of the 18 MV LINAC. It was demonstrated that the 10 μm SOI microdosimeter with 10B4C converter is suitable for detection of thermal neutrons with excellent discrimination of gamma, fast and thermal neutron components in the presence of a gamma-neutron pulsed field of an 18 MV LINAC. To reduce the gamma contribution and further improve detection of neutrons in mixed radiation fields, a new 2 μm Mushroom-planar microdosimeter was fabricated and characterised in detail using an Ion Beam Induced Charge Collection (IBIC) technique with 1.78 MeV He2+ ions. It was demonstrated that this 2 μm SOI microdosimeter can be operated in a passive mode. The SOI microdosimeter with the 10B4C converter can be recommended for detection of thermal neutrons for SEU prediction in mixed gamma-neutron field during space missions especially for the Moon mission.