Yam, a monocot, is originated in the Far East and spread westwards. Yams are second to cassava as the most important tropical root crop. They have since evolved independently in the Eastern and Western Hemispheres, and today yams are grown widely in throughout the tropics. A number of species are cultivated for food in the tropics; in certain tropical cultures, notably of West Africa and New Guinea, the yam is the primary agricultural commodity and the focal point of elaborate ritual. Of the estimated 300-600 yam species are available, there are just over half-dozen principal species that are grown for consumption, while others are grown for medicinal purposes. True yams are botanically distinct from the sweet potato which is a dicot, but moist-fleshed varieties of sweet potato are often called yams in the United States. Yams are consumed as cooked starchy vegetables.

Thai yam
Yam can be found all regions of Thailand, but the main application of these yam tubers is only as home and local economic food, not for an industry. Thai yams are grown by planting pieces of tuber, or small whole tubers (‘seed yams') saved from the previous season. Small-scale farmers, the majority of producers, often intercrop yams with cereals and vegetables. Yams are also extraction starch on the commercial-scale when compared with other starch sources (cassava, potato, maize, wheat and sweet potato).