I've just tried to add url-encoded string into link_rewrite manually thru phpMyAdmin and it WORKS! =)
However, it does NOT work if I enter thai letter. It works only if I enter url encoded.
Here is the result:
http://veenafashion.com/th/5-%E0%B9%80%E0%B8%AA%E0%B8%B7%E0%B9%89%E0%B8%AD%E0%B8%9C%E0%B9%89%E0%B8%B2
In the address bar it shows thai letters.