Aligning paragraph inside a tabular
Due to technical reasons (or let's say bidirectional typesetting bugs of XeTeX), you need to put list-like environment inside \parbox or minipage environment. Therefore the solution is:
\documentclass{article}
\usepackage{bidi}
\setRTL
\begin{document}
\begin{tabular}{|p{5cm}|}
\hline
\textbf{item 1:} These are some texts to just fill in the first line.
\tabularnewline
this is the second Item which still needs to be indented
\parbox{5cm}{\leavevmode%
\begin{itemize}
\item item 1
\item item 2
\end{itemize}}
\\ \hline
\end{tabular}
\end{document}
or
\documentclass{article}
\usepackage{bidi}
\setRTL
\begin{document}
\begin{tabular}{|p{5cm}|}
\hline
\textbf{item 1:} These are some texts to just fill in the first line.
\tabularnewline
this is the second Item which still needs to be indented
\begin{minipage}{5cm}
\begin{itemize}
\item item 1
\item item 2
\end{itemize}
\end{minipage}
\\ \hline
\end{tabular}
\end{document}
Are you after something like this?:
\documentclass[a5paper]{article}
\usepackage{tabularx}
\begin{document}
\begin{tabularx}{\textwidth}{|>{\bfseries}lX|}
\hline
Item 1:& These are some texts
just to fill in the first line.
And some more texts
just to fill in the second line.\\
Item 2:& These are some texts
just to fill in the first line.
And some more texts
just to fill in the second line.
\\ \hline
\end{tabularx}
\end{document}
Updated, in the light of more detail in the question:
\documentclass[a5paper]{article}
\usepackage{tabularx}
\begin{document}
\begin{tabularx}{\textwidth}{|>{\bfseries}lX|}
\hline
Item 1:& These are some texts
just to fill in the first line.
And some more texts
just to fill in the second line.\\
& This is the second Item which still needs to be indented
\begin{itemize}
\item item 1
\item item 2
\end{itemize}
\\ \hline
\end{tabularx}
\end{document}
Note that: (a) I've made the major item stub a separate column in the table (Sorry, I don't know whow tabularx works with RTL text); and (b) rather than \tabularnewline
, I've added a table row for the second bit. Although this may not match what you're doing syntactically, I think it might make things a bit more maintainable.
This is how I guess RTL might work:
\documentclass[a5paper]{article}
\usepackage{tabularx}
\begin{document}
\begin{tabularx}{\textwidth}{|X>{\bfseries}l|}
\hline
These are some texts & Item 1:
just to fill in the first line.
And some more texts
just to fill in the second line.\\
This is the second Item which still needs to be indented
\begin{itemize}
\item item 1
\item item 2
\end{itemize}
\\ \hline
\end{tabularx}
\end{document}