#include <Array.au3>
$str = "abc,def(,),ghi,j(,)kl,(,)mno,pqr"
$ar = _split($str)
_ArrayDisplay($ar)

Func _split($str)
    Local $pattern = "([^,]*\(,\)[^,]*)|([^,]*)"
    Local $ret = StringRegExp($str, $pattern, 3), $aOut[1] = [0]
    For $i = 0 To UBound($ret) -1
        If $ret[$i] <> '' Then
            ReDim $aOut[UBound($aOut)+1]
            $aOut[UBound($aOut)-1] = $ret[$i]
            $aOut[0] += 1
        EndIf
    Next
    Return $aOut
EndFunc