The tax ratio is a key indicator reflecting a country's fiscal capacity to finance development and reduce economic inequality. This study aims to comparatively analyze the tax ratio in three ASEAN countries: Indonesia, Thailand, and Vietnam. This study uses qualitative methods, including literature, documents, and data, to obtain a snapshot of the economic and taxation structures, compliance levels, and fiscal policies in the three countries. The analysis shows that Vietnam has successfully increased its tax ratio through administrative reforms and tax base expansion. Thailand excels in personal income tax reform and tax system digitalization. Indonesia has shown increased compliance, but its tariff-focused reforms have not been effective enough to broaden the tax base. These findings have important implications for designing sustainable fiscal policies in the three ASEAN countries.