documentclass{beamer}
usepackage[group-separator={,}]{siunitx}

begin{document}
begin{frame}
    begin{table}
        begin{tabular}{S[table-format=5.0]S[table-format = 1.1]}
            12000             & 1.4 \
            (14000) & 1.2
        end{tabular}
    end{table}
end{frame}
end{document}