This will depend on the reason your thread was deleted, but generally, you cannot re-post a deleted thread, especially without contacting the moderator who deleted it first. When your thread is deleted, you'll receive an alert stating the reason why the thread was deleted. If the thread you posted was a spammed advertisement or a prohibited topic, you will not be able to re-post this thread under any circumstances. Additionally, re-posting threads of that nature will often result in an infraction being issued to your account. However, if you feel that you can remove the rule-violating content from your thread, you can contact the moderator who deleted the thread and ask them if the edited version would be acceptable. In some cases, the moderator may simply edit the rule-breaking bits out of your old thread and undelete it.