my $nfw_oang = qr%    
    (?!\p{IsOang}(?!
        (?:\p{InThaiFinCons}){1,2}    
        (?![\p{InThaiCompVowel}\p{InThaiPostVowel}\p{InThaiTone}])
        (?:\p{InThaiMute})
    ))
%x;