MoreLocale 2 is an application from the Google Play and it will be able to add Vietnamese in any smartphone. Change your AT&T or Sprint android phone default language with this free app. This is a very cool app that allows you to change most smart-phones, to languages like German, Japanese, Spanish, Dutch etc. It works on Xperia S.
* NOTICE * After 4.2 new Jelly Bean, The protection level definition of CHANGE_CONFIGURATION has been changed. If you’re able to use development tools, you can grant the permission manually by ‘pm’ command. If you have SuperUser privilege on your device. MoreLocale 2 could get the permission automatically.You can select more locales via this app. If your locale doesn’t appear, please use custom locale function in menu.