This paper provides the systematic way of forecasting the quality of loans in the corporate and consumer sectors. Using the data in the Thai banking sector from the past 15 years, we were able to pinpoint the main determinants of both the special-mentioned (SM) loans and the non- 27 performing loans (NPL) for both sectors. Although our findings share similarities to the results from the existing literatures on this subject, we were able to determine the important drivers and to tailor-made our prediction for the SM/NPL in each specific sector, corporate and consumer. Our results showed that, although the quality of each type of loans—corporate and consumer—share similar drivers such as factors reflecting excess liquidity and loan growth as well as real GDP growth, there are differences in determinants as well. Price variables such as oil price and CPI seem to only affect SM and not NPL, for example. These particular characteristics are key to understanding the dynamics of the SM and NPL in each real sector and how they are linked to bank-specific and macroeconomic factors. With these forecasting models, bank supervisors can use the determinants of the quality of loans as an early warning signal to gauge the health of the bank lending business in a forward-looking manner, and, in addition, use them as potential stress-testing tools that link the possible adverse scenarios to the loan quality of the banking sector so as to prepare the appropriate policy in an effective and timely fashion.