Paper Title
The Risk and Return on Investment Ratio Analysis for Decision Making to Invest in Service Sector Securities in Thailand Stock Exchange

This research intended to analyze the risk and return on investment ratio for the decision making to investment in service sector securities in Thailand Stock Exchange. This research analysis is based on the Capital Asset Pricing Model (CAPM) and selected the only 6 Service sectors securities in Thailand Stock Exchange by using the closing price at the end of the month to calculate the return on investment in service sector securities, using monthly Stock Exchange Index to represent the rate of return on investment of the Stock Exchange as well as using monthly average of the 12-month fixed deposit rate from commercial bank to represent the yield of non-risk securities, including by using the Capital Asset Pricing Model to measure the risk and return on investment of securities.From the research result, it was indicated that the service sector securities index risk is lower than the market, which means the fluctuation of the return on investment of securities in this sector is slower than the market rate. However, the yield is higher than the required yield rate (R) by using the theory of CAPM in the Stock Exchange of Thailand. On a separate basis, securities in the medical sector (Health) and securities in the hotel and tourism sectors (Tourism) had the lowest risk that the value of ß is 0.309 compared to the market. The securities with the highest risk, including the entertainment and recreation business securities (Media), the ß value is at 0.85. Future studies should study the flow of the Fund (Fund Flow) which affect the investment in particularly in Thailand stock market that can determine the direction of the index, furthermore. If foreign market investors were to sell them or buy shares, the movement of the SET Index will rise sharply immediately moreover the arising of many factors was expecting to influence the yield of the securities, therefore the Technical and Fundamental Analysis should be implemented. In terms of industry analysis, in order to measure how reliable, the company securities price is, the use of the company securities price comparison towards the credibility of the securities index in that sector was implemented Keyword - Yield, Risk, Service Sector Securities