By default “remarks” form field is in textarea field type, to change the signature “remarks” form field by using filter hook.

Copy and paste this code and add it the theme functions.php file

 
    function my_custom_remarks( $fields ){
        $fields['remarks']['field'] = 'select';
        $fields['remarks']['options'] = array( 'In route', 'outbound', 'In coming' );
        return $fields;
    }
    add_filter( 'wpcpod_signature_field_list', 'my_custom_remarks');