Background. Etiologies for acute kidney injury (AKI) vary by geographic region and socioeconomic status. While considerable information is now available on AKI in the Americas, Europe and China, large comprehensive epidemiologic studies of AKI from Southeast Asia (SEA) are still lacking. The aim of this study was to investigate the rates and characteristics of AKI among intensive care unit (ICU) patients in Thailand. Methods. We conducted the largest prospective observational study of AKI in SEA. The data were serially collected on the first 28 days of ICU admission by registration in electronic web-based format. AKI status was defined by full Kidney Disease: Improving Global Outcome criteria. We used AKI occurrence as the clinical outcome and explored the impact of modifiable and non-modifiable risk factors on the development and progression of AKI. Results. We enrolled 5476 patients from 17 ICU centres across Thailand from February 2013 to July 2015. After excluding patients with end-stage renal disease and those with incomplete data, AKI occurred in 2471 of 4668 patients (52.9%). Overall, the maximum AKI stage was Stage 1 in 7.5%, Stage 2 in 16.5% and Stage 3 in 28.9%. In the multivariable adjusted model, we found that older age, female sex, admission to a regional hospital,medical ICU, high body mass index, primary diagnosis of cardiovascular-related disease and infectious disease, higher Acute Physiology and Chronic Health Evaluation II, non-renal Sequential Organ Failure Assessment scores, underlying anemia and use of vasopressors were all independent risk factors for AKI development. Conclusions. In Thai ICUs, AKI is very common. Identification of risk factors of AKI development will help in the development of a prognostic scoring model for this population and should help in decisionmaking for timely intervention, ultimately leading to better clinical outcomes.