Cassava root in a collection depot in Sai Yok district , Kanchanaburi , about 200 km west of Bangkok , Thailand , 24 April 2008 . Thailand is the worlds largest cassava exporter and in the last 12 months the export price of Thai tapioca starch has risen by 80 percent . Thailand is also the world ' s largest rice exporter . Cassava provides an edible starchy root , high in carbohydrates making it the third largest source of carbohydrate for human food in the world . Cassava is a vital staple for about 500 million people and irs leaves are also eaten as a vegetable . Tapioca is produced from treated and dried cassava root and is high in starch and used in cooking . Thailand ' s Prime Minister Samak Sundaravej has criticised the World Bank and United Nations for criticising biofuel - producing nations for soaring food prices while sparing oil exporters as the world faces warnings of a global food crisis . EPA / BARBARA WALTON < 저작권자 ⓒ 2007 연 합 뉴 스 . 무단 전재 - 재 배포 금지 . >