Hi,
I think there's no "normal" way to do this. You can edit a thread and just delete the content and subject/topic and maybe write '(deleted)' as subject/topic and content, but as said, I think there is no better way... well... maybe you could report your own post and ask for it's removal. Otherwise try editing it and go into more option and look, if you can find anything.
Hope I could help you somehow 
Greeting 
