Kusura bakmayın, düşünemedim. Kodlarım aşağıdaki gibidir.

index.php:
<div class="modal fade duzenle" id="edit-modal">

<div class="modal-dialog modal-lg" role="document">
    <div class="modal-content">
        <div class="modal-header">
            <h5 class="modal-title pl-3" id="exampleModalScrollableTitle">Markayı Düzenle</h5>
            <button type="button" class="close" data-dismiss="modal" aria-label="Close">
                <span aria-hidden="true" class="text-white">&times;</span>
            </button>
        </div>
        <form method="post" id="frmedit" enctype="multipart/form-data">
            <div class="modal-body pre-scrollable">
                <input type="hidden" name="id" id="id" class="form-control">
                <div class="form-group form-float mt-3">
                    <div class="form-line">
                        <input type="text" class="form-control" id="duz_sira" name="duz_sira" required>
                        <label class="form-label">Sıra</label>
                    </div>
                </div>
                <select class="form-control" name="duz_durum" required>
                    <option>Durum Seçiniz</option>
                    <option value="aktif">Aktif</option>
                    <option value="pasif">Pasif</option>
                </select>
            </div>
            <div class="modal-footer">
                <button type="button" class="btn bg-grey waves-effect iptal-butonu" data-dismiss="modal">İptal</button>
                <input type="submit" id="update" class="btn bg-purple waves-effect kaydet-butonu" value="Kaydet">
            </div>
        </form>
    </div>
</div>

</div>

<script type="text/javascript">

$(document).ready(function () {
    /********************** MODAL AÇMA **********************/
    $(document).on('click' , '.bn-edit' ,function(){
        var id = this.id;
		console.log("id:"+id+",type:marka");
        $.ajax({
			type: "GET",
			url: "read.php?id="+id+"&type=marka",
            success:function(response){
                $("#edit-modal").modal('show');
				$.each(response, function(key, value) {
					console.log("key:"+key+",value:"+value);
				})
                $("#duz_sira").val(response.sira);
                $("#duz_durum").val(response.durum);
                $("#id").val(id);
            }
        });
    });
});

</script>

read.php:
case "marka":

        if(isset($_REQUEST["id"])){
            $result = $mk_db->oku("marka", " id='$id' ", "", "", "");
            if(!empty($result)) {
                $responseArray["marka_adi"] = $result[0]["marka_adi"];
                $responseArray["resim"] = $result[0]["resim"];
                $responseArray["durum"] = $result[0]["durum"];
                $responseArray["sira"] = $result[0]["sira"];
                echo json_encode($responseArray);
            }
        }
        break;