AIM: To determine the risk factors and time to non-arteric ischemic optic neuropathy (NAION) occurrence among Thai type 2 diabetes mellitus (T2DM) patients. METHODS: A retrospective review of 266 newly diagnosed T2DM cases at Rajavithi Hospital between 2007 and 2016 was conducted to determine time to occurrence of NAION and evaluate associated risk factors. RESULTS: Hypertension and dyslipidemia were the most common pre-existing vascular diseases and there was a significant male predominance in the NAION group. The mean age of the NAION group was significantly higher than that of the group without NAION. A higher proportion of subjects in the NAION group had hypertension, dyslipidemia, high diastolic blood pressure, smokers, and had a small cup-to-disc ratio (CDR). Higher levels of triglycerides and low-density lipoprotein-cholesterol in the group with NAION. Fifty-five patients among 266 participants (20.68%) developed NAION during a mean follow-up time of 81.26±25.04mo. In a multivariable logistic regression analysis, dyslipidemia (OR=8.36, 95%CI, 3.447–20.273, P<0.001), high low density lipoprotein levels (OR=1.017, 95%CI, 1.004–1.029, P=0.009), and small CDR (OR=11.92, 95%CI, 4.477–31.741, P<0.001) were significant risk factors for NAION development. Smoking was the strongest predictive risk (OR=12.843, 95%CI, 3.959–41.659, P<0.001). Vascular complications of T2DM and aspirin were not associated with NAION. CONCLUSION: T2DM patients with dyslipidemia or a small CDR should be carefully followed up as they are at increased risk of developing NAION.