mysql question

[Princeton]

Is there a better way to rewrite (optimize) this sql code? (NOTE: Some parts have been ommitted):
[sql]SELECT thread.threadid, thread.title, thread.postusername, thread.postuserid, thread.lastpost, forum.forumid
FROM thread AS thread
LEFT JOIN forum AS forum ON ( thread.forumid = forum.forumid )
WHERE thread.forumid
IN ( 25, 57, 223, 56, 88, 55, 58, 59, 60, 61, 63, 64, 65, 66, 67, 68, 69, 70, 71, 72, 73, 74 , 75, 76, 77, 78, 79, 80, 81, 89, 116, 178, 217, 218, 219, 220, 221, 222, 226, 231, 229, 227, 228, 230) AND thread.visible =1
ORDER BY lastpost DESC
LIMIT 16 [/sql]
The reason I ask is because it can take some time if rows > 50,000

thank you