This paper presents the mathematical model which considered the facility location problem for local drug stores for psychiatric disorders in Thailand. Due to the increasing number of patients in the hospital, Thailand has initiated several strategies and projects in order to reduce congestion in the hospital. A medicine distribution system is one of the projects to cope with hospital overcrowding. The initiative project especially focuses on the psychiatric patients who live in rural areas which is hard to access psychiatric services. The idea of this project is to select local drug store representatives as medicine distributors, so that psychiatric patients can directly go to pick up their medicine from those local drug stores according to hospital’s prescriptions. Therefore, this paper studies on the design of a drug delivery system between hospital and local drug stores, and 7 provinces in Northern Thailand are chosen as a case study. The goal of a mathematical model is to determine the location of local drug store representatives that will be medicine distribution hubs for psychiatric patients. The objective of the model is to minimum number of local drug store representatives that can serve all patients in the system. The model is solved using LINGO 14.0 and the experimental results showed that the optimal solutions can be obtained for all provinces.