The selection of candidates at some enterprises and the assignment of suitable personnel after recruitment have not been well implemented and remain somewhat subjective. This easily leads to feelings of discouragement, ineffective work, and ultimately inevitable resignation. To solve this issue, the study proposes the application of the Analytic Hierarchy Process (AHP) to rank the criteria or solutions of a problem by prioritizing them for selection, combined with the Simulated Annealing (SA) algorithm. This mathematical model will support the reasonable assignment of personnel. The combination of these two techniques aims to complete the process of selecting and assigning personnel, which is considered not to have been done before. To demonstrate the effectiveness of this combination, an experiment was conducted to select and assign employees in the Human Resource Management (HRM) department at a Thai manufacturing enterprise. The results showed that candidates were selected and personnel were assigned with accurate and rapid quantitative evaluation. The rate of changes or resignations after one year of observation was not recorded, indicating the feasibility of applying this in practice.