<script>
var myJsonString = <?php echo json_encode($cus_group) ?>;
$(document).ready(function() {
  $("#cus_group").kendoDropDownList({
    dataTextField: "cus_type_name",
    dataValueField: "cus_type_id",
    dataSource: myJsonString
  });
});
</script>

ผลลัพธ์

<script>
    var myJsonString = [{"cus_type_id":"1","cus_type_name":"Group 1","cus_type_description":"Group 1"},{"cus_type_id":"2","cus_type_name":"Group 2","cus_type_description":"Group 2"}];
      $(document).ready(function() {
        $("#cus_group").kendoDropDownList({
          dataTextField: "cus_type_name",
          dataValueField: "cus_type_id",
          dataSource:myJsonString
        });
      });
    </script>

ทำแบบนี้ แล้วถ้าข้อมูลเยอะขึ้นเรื่อยๆ จะมีปัญหาไหมครับ