An ethnobotanical study of the genus Smilax in Thailand and its botanical authentication for Hua-khao-yen crude drugs oleh Pithkanda Pansumrit, Thanika Pathomwichaiwat, Pornchai Kladwong, Suppachai Tiyaworanant, Varangrat Nguanchoo, Bhanubong Bongcheewin