A BF3 gas-filled proportional detector, or neutron counter, can be used for detecting atmospheric neutrons, which are created from (primary) cosmic rays colliding with air molecules. These (secondary) atmospheric neutrons can produce tertiary neutrons by interacting with other objects, such as buildings and ground. The number of produced tertiary neutron depends on the type of materials and the energy of the atmospheric neutrons. Neutron counters are usually operated inside a lead producer and a polyethylene reflector, in the standard neutron monitor configuration; when used with no producer and no reflector, they can be called bare neutron counters. The sensitivity of a bare neutron counter as a function of distance from the detector has never been studied in detail. Therefore, we use Monte Carlo simulations to calculate the neutron counter sensitivity inside the Princess Sirindhorn Neutron Monitor (PSNM) station at Doi Inthanon, Thailand (18.59˚N, 98.49˚E, 2,560m altitude) at different atmospheric neutron energies (1keV - 1GeV). We are interested in two conditions: dry and wet (5% humidity) ground. Here we present the result of our study as compared with previous simpler simulations.