The primary purpose of this dissertation is to investigate the behavior of the stock returns over long horizons using the data from the Stock Exchange of Thailand. In Chapter 2, the long-run relationship between stock prices and dividends is investigated. The null hypothesis of no cointegration using both the Engle-Granger and Johansen cointegration tests cannot be rejected; however, when the structural break is addressed, the Gregory-Hansen cointegration test reports the significant evidence of the long-run relationship between stock prices and ...