This research aims to study the relationship between tax planning & performance and the stock prices & dividend payments of companies listed on the Stock Exchange of Thailand SET100 group. It was conducted by collecting information from financial statements annual reports and the information registration forms (Form 56-1) of 69 companies from 2015 to 2019. Descriptive statistics and inferential statistics were used for data analysis including correlation analysis and multiple regression analysis. The study results show that the return on equity ratio (ROE) book value per share (BV) and earnings per share (EPS) ratio positively correlated with the stock prices. The corporate income tax rate to total assets (TAX/ASSETS) the return on total assets (ROA) the return on equity (ROE) and the book value per share (BV) ratio were positively correlated with the dividend yield (DY) ratio. The earnings per share (EPS) ratio had a negative correlation with the dividend yield (DY) ratio and the effective corporate income tax (ETR) ratio had a positive correlation with the dividend payout ratio (DP) with a statistical significance at 0.01 and 0.05 levels.

The objective of this research is to study the companies listed on the Stock Exchange of Thailand Property and Construction Group on the relationship between corporate governance; namely the percentage of shares held by executives proportion of independent directors size of the board of directors management responsibilities of the chairman and the proportion of attendance at board meetings and 1) the operating result i.e. the return on total assets return on equity return on sales and earnings per share and 2) tax planning including the ratio of tax expenses to accounting profits before income tax and tax rate per total asset. The secondary data collected from the financial statements and the registration statement (Form 56-1) from year 2014 to 2018 in total of 71 companies is analyzed using descriptive statistics including mean and standard deviation and inferential statistics such as correlation analysis and multiple regression analysis. The research results showed that corporate governance including the shareholding percentage held by management management responsibilities of the chairman and the proportion of attendance at the Board meetings has a positive relationship with tax planning (Tax rate to total assets) with statistical significance at the level of 0.01 and 0.05. There is also a positive relationship between the operating results including the return on total assets and tax planning (Tax rate to total assets) with statistical significance of 0.01.

The purpose of the study on Knowledge and Understanding of Personal Income Tax Planning is to study the knowledge and understanding on personal income tax problems and obstacles of individual taxpayers regarding internet tax filing. The study compared the level of knowledge understanding and planning of personal income tax of the sample with different demographic factors. The questionnaire was used as a tool to collect data. A total of 410 samples were used for one-way analysis of variance (One Way ANOVA) and compared by Least-Significant Different (LSD). The research found that the overall understanding of personal income tax planning was moderate. The most knowledgeable issues were net income taxable income expenses and tax reduction which were in high level. Secondly the issue of “the personal income tax rate is a progressive tax rate” was in a very high level. The lowest level was “each type of assessment has different deduction rates”. “Type 1 income has the least expense deductible rate” was in moderate level. In conclusion different gender occupation and education levels have statistically significant knowledge and understanding on tax planning.