[Eikinskjaldi]

that query wont show the latest 10.

You will need to add an order by post.dateline (or postid, I guess) desc at the end. Also, you should use join to join tables, not where

PHP Code:

"SELECT post.*
FROM ". TABLE_PREFIX ."thread AS thread,
JOIN ". TABLE_PREFIX ."post AS post
USING (threadid)
WHERE
    thread.forumid = XX AND
    post.visible = 1
ORDER BY
    post.postid DESC
LIMIT
    10"