%!TEX pdflatex

\documentclass{article}
\usepackage[a5paper]{geometry}
\usepackage{tcolorbox}
\usepackage{lipsum}
\tcbuselibrary{skins}

\begin{document}

\begin{tcolorbox}%
	[%
	enhanced,size=small,frame empty,interior empty,sharp corners,top=2mm+2mm,left skip=0.5cm,underlay boxed title={\filldraw[draw=none,blue!10,line width=0.5mm] (frame.north west) rectangle (frame.south east);\draw[blue,line width=0.5mm] (frame.north west) -- (frame.south west) ;},attach boxed title to top left={xshift=-0.5cm,yshift=-\tcboxedtitleheight+2mm},title={\vphantom{(qM)}Mon titre},
	boxed title style={interior empty,size=small,boxsep=0.5mm,frame code={\filldraw[red!75!black,rounded corners=0.5mm] (frame.north west) |- ([xshift=0.4cm]frame.south west) --++ (0.225cm,-0.175cm) |- (frame.south east) -- (frame.north east) -- cycle ;}},fonttitle=\small\bfseries\sffamily
	]
	\lipsum[1]
\end{tcolorbox}

\end{document}