ok lựa chọn giao diện hiện thị cho 1 category trong wordpress file \wp-includes\template.php trong hàm get_single_template()

template.php

function get_single_template() {
	$object = get_queried_object();

	$templates = array();

	if ( ! empty( $object->post_type ) )
		$templates[] = "single-{$object->post_type}.php";

//	$templates[] = "single.php";
    $the_categories = get_the_category();
                //var_dump($the_categories);exit();
    if ($the_categories[0]->category_nicename=='rem_romain') {
    $templates[] = "rm_theme.php";
    //echo '123';exit();
}  else {
    $templates[] = "test_content_single.php";
    //echo '321';exit();
}
	
	return get_query_template( 'single', $templates );
}