From A Wiki of Ice and Fire
Yi Ti is a region in eastern Essos. It is located east of Qarth and the Bone Mountains and is bordered by the Jade Sea to the south. Nearby islands in the Jade Sea are Leng and the Isle of Whips. North of Yi Ti are the Great Sand Sea, the Shrinking Sea, and the Bleeding Sea; a great river runs south from the Bleeding Sea through Yi Ti to the Jade Sea. Located east of Yi Ti are the Mountains of the Morn, the Shadow Lands, and Asshai.
The land of Yi Ti has thick, green patchwork farmland and a verdant rainforest. Rumors have it that basilisks roam the jungles of Yi Ti. Two known cities in Yi Ti are Yin and Jinqi along the Jade Sea coast. The city of Asabhad, possibly located in Yi Ti, is located at the western edge of the forest near the Bone Mountains and the Jade Gates. There is a trade route from Asabhad to Yin along the coast of the Jade Sea.
Men from Yi Ti are bright-eyed and wear monkey-tail hats.
A Game of Thrones
In the Western Market of Vaes Dothrak Daenerys Targaryen sees a fat cloth trader from Yi Ti haggling with a Pentoshi over the price of some green dye, the monkey tail on his hat swaying back and forth as he shakes his head. 
A Clash of Kings
In Qarth Xaro Xhoan Daxos tries to entreat Daenerys to accompany him on his pleasure barge to the Jade Sea. He suggests that they journey around Yi Ti to search for the dreaming city of poets and to sip the wine of wisdom from a dead man's skull.
A Feast for Crows
A Dance with Dragons
References and Notes