[XeTeX] Linebreaks in Thai-text

[BN]

Hi,
needing a little help:

after copying text from a Thaiwebsite and pasted it in Texshop -I have 
used these minimal settings:

\documentclass{minimal}
\usepackage{xltxtra, polyglossia}

\setmainlanguage{german}
\setotherlanguage[numerals=thai]{thai}

\newfontfamily\thaifont[Script=Thai]{Waree}

\begin{document}
\textthai{here comes the copy of the Thaiwebsite}.

\end{document}-

I got a pdf-file but  most of the textlines on the right side has been cut off. 

What is the solution?

Bernd