Our empirical results contribute to the literatures on the usefulness of historical
accounting information in predicting future stock returns. While prior research finds that
financial ratios are associated with future stock returns, our study, together with Piotroski
(2000) and Mohanram (2005), provide empirical evidence suggesting that the investorfriendly
composite scores constructed based mainly on historical accounting information can
be used to choose stocks to invest to earn positive abnormal returns and they can be applied
for not only high or low BM firms, but also for all firms. Moreover, our results contribute to
the literatures on the efficient market hypothesis. Specifically, our results that investors can
use publically available, historical accounting information to choose stocks and earn
abnormal stock returns seem to suggest that Thai stock markets are not semi-strong form
efficient.