This research aims to explore the impact of internal control quality on the market
value of real estate companies listed on the Stock Exchange of Thailand using secondary data of
110 companies over a 3-year period from 2021 to 2023. The price-to-sales ratio (P/S) is set as
the dependent variable, while internal control quality (CG) is converted into a categorical
variable based on the corporate governance score. In addition, the variables of operating profit
to revenue (OPM), business size (Log Total Assets), business age, and financial risk (Debt-toEquity) are controlled. The data are analyzed by using multiple regression.The model test results
indicate that the model is appropriate, as shown by a statistically significant F-statistic. Internal
control quality exhibits a significantly negative relationship, suggesting that companies with
higher governance scores may be undervalued within the Thai real estate industry. Operating
profit has a positive influence on the price-to-sales ratio, while both firm size and financial risk
also show significant effects positive for firm size and negative for financial risk. The effect of firm
age is not statistically significant. An examination of multicollinearity reveals acceptable variance
inflation factor values, and the Durbin-Watson statistic confirms the absence of autocorrelation
issues. The findings suggest that operating efficiency, capital structure, and firm size remain key
drivers of market valuation, whereas internal control quality may exert a short-term negative
impact under Thailand's regulatory conditions. These results have implications for executives in
shaping governance policies that balance strict oversight with operational flexibility. From a
theoretical perspective, the study contributes to the understanding of internal control’s role in
the real estate sector of developing economies and recommends future research to incorporate
ESG disclosure variables and long-term dynamic analysis to validate the observed relationships.