Recent evidence suggests that there might be an asymmetric process of adjustment towards the long-run equilibrium in the government revenue-spending nexus. In this paper, the long-run relationship between government revenue and spending is examined in the case of Thailand using annual data over the period 1991โ2019. Specifically, this is an attempt to determine whether this long-run relationship is linear or nonlinear. In doing so, both linear and nonlinear cointegration tests are employed. The empirical results suggest that the positive long-run relationship between revenue and spending is linear and stable when revenue is the dependent variable. By estimating the TAR and MTAR models, evidence of a nonlinear revenue-spending relationship is not found. Therefore, there does not seem to be asymmetric adjustment toward the long-run equilibrium. The results of causality tests based on the estimated ECMs of linear cointegrating equations show no causality between revenue and spending in the short run, supporting the fiscal institutional separation hypothesis. In the long run, there is unidirectional causality running from government spending to revenue, which supports the fiscal spend-and-tax hypothesis. [ABSTRACT FROM AUTHOR]