Kassod Tree (Cassia siamea) Senna siamea (Thai: ???????? khilek) also known as Kassod Tree Cassod Tree and (incorrectly) as Cassia tree is a legume in the subfamily Caesalpinioideae. It is native to South and Southeast Asia although its exact origin is unknown. It is a medium-size evergreen tree growing up to 18 m with beautiful yellow flowers. It is often used as shade tree in cocoa coffee and tea plantations. In Thailand it is the provincial tree of Chaiyaphum Province and some places in the country are named after it. Leaves are alternate pinnately compound with slender green-reddish tinged axis and 6 to 12 pairs of leaflets on short stalks rounded at both ends.