Hello Philippe Blankert - Thanks for your interest in Unicode...
http://www.burmese-dictionary.org/tastatur.php?terme=hotel&termb=%5Bkdw%2Cf&id=2970
That page isn't in Unicode at all, it's an 8859-1 encoded page. That's part of the problem.
Then, the Burmese characters on the page are all *images*, and when you click the buttons to type into the field, it seems to send ASCII text to the input field.
And the WWin_Burmese1 font, which I just downloaded to check, is an "ASCII-hack" font that is not encoded in Unicode.
Hope that helps. Rick