This study explored the role of dentate status and dental caries on diabetes-related complications among patients with type 2 diabetes mellitus (T2DM). A hospital-based cross-sectional design was applied to collect data on diabetic patients attending integrated services for non-communicable diseases and oral health at a public hospital in Thailand. Diabetic complication outcomes included diabetic eye and foot complications and chronic kidney disease (CKD). The main independent variable of dentate status and dental caries was classified into three categories: dentate and caries-free, dentate with caries, and edentulous. The relationships were evaluated through epidemiological models depicted by directed acyclic graphs (DAGs). Multivariable Poisson regression with robust standard errors was applied to estimate prevalence ratios (PR) according to DAGs. Among 438 patients with T2DM, 62.8% were women, and an average age was 63.6 years. Most patients were dentate with dental caries (70.1%), and 8.2% were edentulous. Prevalence of diabetic foot complications and CKD were 37.1% and 10.1%. Six patients had eye complications. Regarding CKD outcome, PR estimates from univariable and multivariable models were 0.94–1.12 for the dentate with caries group and 1.67–2.31 for the edentulous group, all with non-significant P values. Regarding foot complication outcome, PR estimates were 1.10–1.12 for the dentate with caries group and 1.26–1.37 for the edentulous group, all with non-significant P values. Though not statistically significant, the magnitude and direction of PR suggested a possible hypothesis that, among patients with T2DM, edentulism might be related to a higher prevalence of CKD and diabetic foot complications as compared to being dentate and caries-free.