If you load thmstyle
, the \theoremstyle
declarations are ignored; moreover \newtheorem*
is invalid.
The documentation of thmbox
is not very clear; however, you can emulate the styles of amsthm
quite easily:
\documentclass{scrreprt}
\usepackage[S]{thmbox}
\thmboxoptions{S,bodystyle=\itshape\noindent}
\newtheorem[S]{lem}{Lemma}[section]
\newtheorem[S]{thm}[lem]{Theorem}
\newtheorem[S]{cor}[lem]{Corollary}
\newtheorem[S,bodystyle=\upshape\noindent]{defi}{Definition}
\newtheorem[
S,
bodystyle=\upshape\noindent,
headstyle=\itshape Remarks and Extensions
]{rem}{}
\begin{document}
\chapter{Title}
\section{Title}
\begin{lem}
Something
\end{lem}
\begin{thm}
Something
\end{thm}
\begin{cor}
Something
\end{cor}
\begin{rem}
Remark
\end{rem}
\begin{defi}
A definition
\end{defi}
\end{document}
\documentclass{...}
and ending with\end{document}
.