A key component of nursing practice, accurate pain evaluation is essential to effective post-operative pain treatment. This research investigates the variables affecting Thai nurses' judgments on pain treatment as well as their experiences with post-operative pain assessment. Data were gathered via in-depth interviews with nurses employed in surgical units across Thailand using a qualitative methodology. Based on organizational limitations, patient expressions, and cultural norms, nurses use both clinical standards and their own discretion. Time constraints, a lack of resources, and differences between patients' stated and actual pain levels are among the difficulties. Nurses showed flexibility in customizing pain management techniques for each patient in spite of these obstacles. This research emphasizes the need of systemic support and focused training to improve the efficacy of post-operative pain treatment. Policymakers may enhance patient outcomes and pain assessment procedures in a variety of healthcare settings by taking into account these experiences