\usepackage{threeparttable}

\begin{table}[!htbp]
    \centering
        \caption{...}
    \begin{threeparttable}
        \begin{tabular}{l l l}
            \hline
            A & B & C \\
            \hline
            a & b & c \tnote{*} \\
            \hline
        \end{tabular} \label{tab_name}
\begin{tablenotes}
     \footnotesize
     \item[*] This is the note.
 \end{tablenotes}
\end{threeparttable}
\end{table}