This study aims to develop an internal control model for the finance and procurement functions of Sisaket Rajabhat University under the COSO framework to enhance fiscal transparency and sustainability. A mixed-methods sequential design was employed, consisting of (1) a quantitative assessment of internal control levels among 18 finance and procurement staff, (2) in-depth interviews with seven key informants, and (3) model development and expert validation. Quantitative data were analyzed using descriptive statistics, while qualitative data underwent thematic content analysis. This study employed a three-phase, mixed-methods approach. Phase 1 was a quantitative study utilizing a questionnaire based on the five components of the COSO framework. The participants were 18 officers responsible for treasury and procurement operations. Data were analyzed using descriptive statistics, including frequency, percentage, mean, and standard deviation. Phase 2 was a qualitative study involving in-depth interviews with executives, department heads, and responsible officers to identify operational problems and potential improvements. Phase 3 focused on synthesizing and developing the model through a focus group discussion and expert validation.