Background: The drastically increasing share of fossil fuel supply to meet the rapidly growing electricity demand resulting in increasing Carbon dioxide (CO2) emissions, is the major concern in Thailand. In 2015, fossil fuels used in electricity generation in Thailand accounted for around 85.3% of the total electricity generation. Aim: The aim of the study is to analyze carbon dioxide mitigation options under the cleaner supply-side option beyond the Intended Nationally Determined Contribution (INDC) of Thailand. Methods: In this study, the Long-range Energy Planning (LEAP) model is used to analyze the share of electricity generation and CO2 mitigation from four main different scenarios, namely Business-as-Usual (BAU), Renewable Energy (RE), Carbon Capture Storage (CCS), and Carbon Tax (CT) scenarios during 2015 to 2050. The BAU scenario is constructed following the power development targets of the Power Development Plan in 2015. Results: The results illustrate that in the BAU scenario, electricity generation and carbon dioxide emissions from the power sector will increase by 57.7% and 37.3%, respectively in 2050 as compared to 2015. The imposition of carbon tax of $20/tCO2 from 2020 and an increase to $500/t CO2 by 2050 will have a high potential to reduce CO2 emissions from the power sector as compared with other scenarios. Conclusion: Results show that except for the RE scenarios considering the lower share of solar and biomass, all scenarios would help Thailand in achieving the target of INDC by 2030. Results provide that the share of imported electricity is higher with the imposition of carbon tax as compared to the scenarios with the promotion of renewable energy, CCS and EV technology.