응용하면 될 듯합니다^^

<?php
global $wpdb;

$board_id = 1; // 게시판 ID 입니다.
$results = $wpdb->get_results("SELECT `comments`.* FROM `{$wpdb->prefix}kboard_comments` AS `comments` LEFT JOIN `{$wpdb->prefix}kboard_board_content` AS `content` ON `comments`.`content_uid`=`content`.`uid` WHERE `content`.`board_id`='$board_id' ORDER BY `comments`.`uid` DESC LIMIT 10");

foreach($results as $row){
    $comment = new KBComment();
    $comment->initWithRow($row);
    echo "<p>{$comment->content}</p>";
}
?>