GWT/GXT UTF-8

One of my project require to use Thai character (UTF-8).
The solution is very simple. In order to use internationalized characters, make sure that the host HTML file contains the charset=utf8 content type in the meta tag in the header:

<meta http-equiv="content-type" content="text/html;charset=utf-8" />

Source : https://developers.google.com/web-toolkit/doc/latest/DevGuideI18n#DevGuideStaticStringInternationalization