I have trouble with sorting my index since it is in Vietnamese. I know, this question has been asked already but the problem is that I don't really understand the answer - it seems so complicated... I am using the MiKTeX distribution on Windows and I don't really get the idea of xindy, texindy etc. I have no idea how to implement that and make it run properly. Does anyone know if this has been somewhere explained in basic language or could someone possibly tell me please (as simply as possible) what to put where so that it works?
\documentclass[12pt,oneside,titlepage,headings=small,makeidx]{scrbook}
\usepackage{scrpage2}
\usepackage{cmap}
\usepackage{ulem}
\usepackage[utf8x]{inputenc}
\usepackage[vietnam,polish,english,ngerman]{babel}
\usepackage[T5,T1]{fontenc}
\usepackage{longtable}
\usepackage{lmodern}
\usepackage{makeidx}
\usepackage[columns=2,itemlayout=abshang]{idxlayout}
\usepackage{etoolbox}
\newcommand*\de{\fontencoding{T1}\selectfont\selectlanguage{ngerman}}
\newcommand*\en{\fontencoding{T1}\selectfont\selectlanguage{english}}
\newcommand*\pl{\fontencoding{T1}\selectfont\selectlanguage{polish}}
\newcommand*\vn{\fontencoding{T5}\selectfont\selectlanguage{vietnam}}
\makeindex
\setlength{\parindent}{0pt}
\setlength{\parskip}{1ex plus 0.5ex minus 0.2ex}
\renewcommand*{\chapterheadstartvskip}{\vspace*{-\topskip}}
\clearscrheadings
\ihead[]{}
\chead[]{}
\ohead[]{\sffamily\headmark}
\ifoot[]{}
\cfoot[]{}
\ofoot[\pagemark]{\sffamily\pagemark}
\pagestyle{scrheadings}
\begin{document}
\frontmatter
\title{\pl xxxxxxxx}
\subtitle{\pl xxxx}
\author{\pl xxxxxx}
\date{}
\publishers{xxxxxxxxx\\ \copyright{} 2015}
\maketitle
\pl \tableofcontents
\mainmatter
Here comes plenty of text.
\index{\vn giá}
\index{\vn gạo}
\index{\vn ạ}
\index{\vn khi}
\index{\vn cho}
\index{\vn được}
\index{\vn trong}
\index{\vn ứng}
\index{\vn trang}
\index{\vn ô}
\index{\vn dưới}
\index{\vn trước}
\backmatter
\clearpage
\addcontentsline{toc}{chapter}{INDEKS}
\printindex
\end{document}
And this is being produced:

As you can see, all the special characters are being thrown out to the beginning of the alphabet.
This problem has already been discussed i. a. here. But I don't get it. It's too complex...
