The objective of this study is to estimate the daily extreme precipitation distribution in an Asian monsoon region considering orographic precipitation in mountainous areas. For this purpose, the APHRODITE data set and precipitation observations from 150 raingauges throughout Thailand were used as the main input. First, a bias-correction for underestimated precipitation in the APHRODITE data set was conducted based on the raingauge data. Secondly, a frequency analysis for estimating the extreme precipitation for different return periods was performed based on the bias-corrected APHRODITE data set and the raingauge data. For taking orographic precipitation effect into account, a regression relationship between the calculated extreme precipitation, elevation and latitude was developed using 150 raingauge data. Our results show that when orographic rainfall was incorporated, the extreme rainfall distribution was improved to show the characteristic of rainfall in mountainous areas.