Are you unlucky user of Windows XP English with clean install?
If yes, then probably you cannot see Thai characters in Spark text components (e.g Spark Label) in the following demo:
Code listing: http://gist.github.com/390993
New Flex Spark Label to display text uses the new Flash Text Engine (FTE) introduced in Flash Player 10. And that’s true, FTE brought many very useful new features (text subscript, bidirectional text to name a few) that were previously impossible to achieve with older flash.text.TextField object, but I’ve learned recently that FTE can fail to display Thai characters under Windows XP clean install.
Eric Y Muller explains the technical details at Adobe forums:, why FTE cannot use neither Tahoma nor Microsoft Sans Serif standard Windows XP fonts as device fallback to display Thai characters.
The only workaround for this issue for the frustrated user would be to insert original CD with Windows XP install and install Thai language support using “Regional and Language Options” control panel. But this would impossible to achieve for the anonymous employee that works for trans-global corporation without admin access account %-)
As for the developer of the Flash application we can always embed font into Flash app that contains Thai characters, but this will impact the overall bytesize of the resulting SWF file.
In 2010, Windows XP remains highly relevant OS. Various stat counters show that 52% - 64% computer users use Windows XP. Thus it is very important for any Flash application to play nice under this OS without an hassle.