Background: : There were the conflicted results of the association of ASA, metformin or statin and risk of cancer in the previous studies. This is a population-based study in Thai population which aims to investigate the association between these drugs and the risk of cancer. Methods: A population-based retrospective study was done in Electricity Generating Authority of Thailand (EGAT) 1 and 2 databases which have been contained the 27-year and 15-year follow-up time, respectively. This database composed of the clinical characteristics, onset of cancer, and history of interested drugs from the questionnaire, together with the laboratory result from January 2002 to December 2015. We adjusted for age, sex, BMI, smoking and alcohol consumption. The incidence rate ratio (IRR) was estimated for the association between incidence of cancer and interested drugs. Results: Among 2508 and 2731 participants in EGAT1 and 2 respectively, the incidence of cancer was 8.3% in EGAT 1 and 3.5% in EGAT 2. From univariate analysis, use of interested drugs was significant associated with increased risk of cancer with IRR 1.74 (P< 0.001) for ASA, IRR 1.54 (P= 0.043) for metformin and IRR 1.64 (P= 0.001) for statin. In multivariate analysis, only ASA showed significant increasing risk of cancer with IRR 1.47 (P= 0.021). There was a trend increasing risk of cancer for metformin and statin users but not significant. Older age, low BMI, and female significantly associated with higher risk of cancer. In sub-group analysis, age and alcohol were significantly increased risk of GI cancer, while ASA use showed a non-significant trend of increasing risk of GI cancer. HBV infection was a strongly risk factor for hepatobiliary cancer and statin use had a trend lowering risk of this cancer but it was not statistically significant. Metformin also showed a non-significant trend of increasing risk of thoracic cancer. Conclusions: ASA use significantly associated with increasing risk of cancer but metformin and statin showed a trend of higher risk of cancer. These drugs may associate with cancer metabolome pathway which maybe an important role of carcinogenesis. However, ASA, metformin or statin use and risk of cancer is needed to confirm in the longer follow-up and larger cohort.