As a member you don't have the ability to remove your threads or posts but a Moderator may be able to remove posts or threads, or lock them and move them to a blocked area (or caged area)depending on the nature of the thread and reasons for removing them.
As a general rule, anything you post online is permanent and recorded somewhere on the internet.
You should be able to edit your post, like if you are worried you put too much personal information or something like that? You could remove that part. Otherwise if it's some other concern you might want to private message one of the mods and tell them what is going on and they could remove the post if necessary.