Um if I'm not wrong, Kara-Tur is still the "official" oriental region of the Forgotten Realms, just like Zakhara is the "official" arabian region.
WotC made Rokugan the official setting of Oriental Adventures, but that doesn't mean that Rokugan suddenly appeared in Faerun. Given that the standard setting for the core rules is actually Greyhawk, it seems more likely that it appeared somewhere on Oerth.
And yup, as dargoth3 suggested, Shou Expatriate is probably your best bet for a chinese-like character in FR. Go with the Shou.