The objective of this research is to study the techniques of profit quality analysis and the consistency of the profit quality with different profit quality analysis techniques; and to compare profit sustainability between large companies and small companies of the industrial energy and utilities group and the petrochemical and chemical group. The data is collected from financial statements and data entry forms (Form 56-1) from 2012 to 2018. A total of 47 companies are analyzed using descriptive statistics including mean and standard deviation; and inferential statistics including multiple regression analysis and analysis of the average difference between 2 groups The research found that in the analysis of the profit quality consistency in all 4 methods there were only 13 companies in the energy and utilities group with consistent quality of profits accounting for 39.39%; and 20 with inconsistent results accounting for 60.61%. In the petrochemical and chemical group there was only 1 company with consistent quality in all 4 methods representing 7.14%; and 13 companies with inconsistent quality representing 92.86%. In addition when comparing the profit sustainability between large companies and small companies it was found that there was no statistical difference in profit sustainability (sig = 0.305> 0.05). When comparing the profit sustainability between energy and utilities group and the petrochemical and chemical group it was found that petrochemical and chemical companies had a higher profit sustainability than the energy and utilities group at statistical significance of 0.01 (sig = 0.009 <0.01).

The objective of this research aimed to study factors affecting earning persistence and firm value of list firms in the stock exchange of Thailand in set 100 Index. The data was collected in 5 years period from 2011 – 2015 which including 213 samples and then analyzed data by using descriptive statistics and multiple regression analysis. The research revealed growth rate of sales current earnings and cash flow for short term investment reflected to earnings persistence. Furthermore this research also shed some light on factors affecting firm value and found that earnings persistence financial risk dispersed ownership structure and discretionary accrual directly affected to firm value. These results provided more information to investors about significant factors for decision making especially discretionary accrual factor. Therefore firms who have low level of earnings management and high level of earning persistence will reflect to future firm value.

This research aims to study the relationship between profitability which included gross margin operating margin net profit margin return on assets return on equity and earnings per share and price to earnings ratio and dividend yield. The data were collected from financial statements and the annual reports of the companies listed on the Stock Exchange of Thailand (SET100). The top three companies selected should yield a maximum registered capital of each business category from the 1st January to the 31st of December during 2012 and 2015. 20 companies were chosen. The statistics used in the data analysis were descriptive and analyzed by arithmetic mean maximum minimum Standard Deviation and Pearson Correlation Coefficients to describe the characteristics of the collected data. The results of the study revealed that profitability gained from the gross margin operating margin net profit margin return on assets and return on equity. The earnings per share ratio were related to the price to earnings ratio and dividend yield at the reliability level of 95% and 99%.