Currently Family Tree Builder Version 6 supports 36 languages and Chinese as other Asian languages are not supported.
The good news is that we are abpout to release Family Tree Builder 7 with totalsupport of UTF-8 languages including Chinese, Japanese and Korean.
Vietnamese is able to be typed into the personal details and displays OK but any output like a Report or family tree UNICODE font is not displayed correctly even when the font is set to a UNICODE font like Tahoma.
Trương is displayed as Tr??ng.
Family Tree Builder V 7.0 downloaded 31/4/2013
I assume this fault exists with the paid versions so will hold off untill reasurance a fix is in place.