This paper explores the macroeconomic effects of inflation targeting in Thailand. Furthermore, this study uses a nonlinear new Keynesian model under the dynamic stochastic general equilibrium framework with price indexation to analyze the monetary policy under inflation targeting in Thailand. The model is estimated using a Bayesian statistic for the Thai economy. It shows that inflation is more stabilized and inflation persistence has fallen after adopting inflation targeting. The paper also indicates that the Bank of Thailand is more responsive to the deviation of inflation from its target using inflation targeting. The key monetary mechanism exists through changes in the real interest rate which affect aggregate demand. It is worth noting that the larger the inflation targeting rate is, the lower the steady state output from its steady state level given no trend inflation.