The primary focus of this thesis is to investigate the impacts of tax reform, energy consumption and financial development on the growth and efficiency of the Thai economy. There are three main objectives, which are (i) to evaluate the impacts of reforms in value added tax (VAT) and corporate income tax (CIT) on the welfare and reallocation of resources across production sectors, (ii) to assess the impacts of personal income tax (PIT) reform on growth of production sectors and redistribution of income across households, and (iii) to measure impacts of financial development on growth and energy consumption and to re-examine the relationship between energy consumption, financial development and growth. These three chapters aim to contribute to our understanding of the Thai economy. The analysis is divided into three main parts to meet the objectives. A static computable general equilibrium is used to study the impact of VAT and CIT in Thailand in first part. The analysis focuses on the change of VAT and CIT rates because these taxes are the first two biggest source of government revenue. In addition, there is no systematic study on such impacts in Thai context before. Interestingly, the changes in tax rates reveal contrasting results in term of the net welfare to households. While an increase in the VAT rate from the current level, 7 percent, generates higher net welfare to society, a reduction of the CIT rate from 30 percent to the lower end of the international range, 20 percent, is a more preferable policy on the basis of economy-wide welfare analysis. For the efficiency in reallocation of scarce resources, we study the impacts of these tax reforms on employment, capital, output, supply and price for each sector of the economy. Most positive impacts from reductions in VAT and CIT rates occur in the agriculture sector, textile sector and mining and quarrying sector as these reduce cost of inputs to producers. On the other hand, the paper industries and printing sector and trade and services sector show a negative impact that might have been protected due to higher taxes in the base scenario. In examining the second objective, the dynamic computable general equilibrium approach is applied in order to evaluate the impacts of changes in personal income tax (PIT) rates on growth and redistribution for 25 periods of the Thai economy starting in 2011 using the latest Input-Output Table for the micro-consistent dataset. This study emphasises the impact of a reduction of PIT rate because this is the latest tax change in Thailand and any change in this tax rate will have a different distribution affect for households in each income threshold. The results show that a reduction in PIT rate is helpful in decreasing disparity in the distribution of income and consumption in both the short and long-terms in Thailand. In particular, this tax policy benefited the poorest households throughout the study period, while the levels of income and consumption of the richest households declined, although the magnitude of changes are smaller from time to time. In addition, this PIT reform increases output, employment and capital stock in every sector, which results in a rise in all macroeconomic variables, especially the levels of investment and GDP. Under balanced budget assumption, the findings report that the drop in PIT revenue can be fully compensated by an increase in revenue from other taxes in a growing economy. The third part of this thesis focuses on the third objective by utilising time series data with autoregressive distributed lag (ARDL) and the Toda-Yamamoto approach to investigate the long-run relationship and the direction of causality between energy consumption, financial development and economic growth. The findings reveal positive and significant short-term and long-term effects of energy consumption and gross fixed capital formation on economic growth, while population growth has negative impact on economic growth. Notably, the ARDL result report positive but insignificant impact of financial development on economic growth. Meanwhile, the Toda-Yamamoto causality test indicates a unidirectional causality running from economic growth to energy consumption. This finding supports the conservation hypothesis and implies that energy conservation policy can be implemented with little or no adverse effect on economic growth. In addition, the causality test reveals a unidirectional causality running from gross fixed capital formation and population growth to energy consumption, a unidirectional causality running from gross fixed capital formation and population growth to GDP. On the other hand, the test indicates the absence of causal relationship between financial development and energy consumption, and between financial development and economic growth thus indicating that these variables evolve independent of each other. Above all, the findings indicate that tax reform and energy consumption play crucial roles in the growth of the Thai economy. These findings will hopefully encourage policymakers to carefully conduct policies related to taxation and energy. For instance, any tax policies proposed should not add an excess burden to taxpayers and potentially disturb the growth of consumption, production, trade, investment and saving. Regarding energy policy, the findings imply that the policymakers can implement a strong energy conservation policy to households and the business sectors without compromising economic growth. This can enable Thailand to become a low carbon society with inclusive growth as stated in the Thailand 4.0 policy and the 20-year National Strategic Plan. This study contributes to the existing literature in three aspects. First, this study is the first study that analyses the economy-wide impacts of changes in VAT and CIT rates on the allocation of labour and capital inputs, on output and supply as well as on prices and rental rates across sectors and on the levels of households' utility and public welfare in Thailand. Second, this study is the first study that presents the magnitude of the economic impacts from tax reforms taking account of complicated economy-wide income and substitution effects over 25 years of the Thai economy. Third, unlike the existing and growing literature on the energy-growth nexus, this study contributes to the literature in this topic by incorporating financial development in the production model and focus on only in the context of the Thai economy. The analytical framework of this study also allows us to investigate the presence of energy-led growth and finance-led growth hypotheses in Thailand.