[readreadread]

Originally Posted by Doitsu

As I suspected, the language code of your .mobi file is set to US English.
Try changing it to Chinese (Taiwan) with Java Mobipocket Metadata editor.

works like a charms! thanks!
unfortunately the conversion is horrible (pdf to mobi) , I am now using duokan (Koreader is buggy and Sigil require to much time for conversion) to read directly this book in pdf but I have spent many hours and I have not figure it out how to change dictionary yet.
Anyone can help ?