Two C-band RADARSAT synthetic aperture radar (SAR) images are used to automatically detect changes that occured in between year 2004 and 2008 due to extensive deforestation, at Gadong River area of Belum-Temengor, Northern region of West Malaysia. Changes are detected by automatically finding the best threshold value of the standard log-ratio image that is derived from the two multitemporal SAR images. Minimum error thresholding is performed using relative entropy method. The result is validated using the difference of two Normalised Difference Vegetation Index (NDVI) images generated from two SPOT-5 images.