1. Introduction
Thailand lies in the tropical zone of Southeast Asia, between latitudes 6° and 21° N and longitudes 98° and 106° E (Fig. 1). The country is bounded in the north, west, and east by mountain ranges, and in the south by the South China Sea and the Andaman Sea, with a total coastline of approximately 2600 km. The climate is mild, with typical Southwest and Northeast monsoons.