I'm adding some fields to attachment edit form by add filter to "attachment_fields_to_edit". The added fields work fine but they are not rendered as the order I added them. Is there a way to order the fields?
Yes there is.
Add css styles for the form or more precisely try to add names in class attribute of the fields. This should help to properly render the order. For this you may want to check the class names of existing fields which was rendered correctly.