As mentioned earlier in the post where I have mentioned the way to mark any chat as Unread, the deletion of a chat thread is not possible in the Facebook messenger application or the main Facebook application (used for the news feeds). But even if you cannot delete the whole thread you can delete certain messages in the chat thread but they are deleted one by one and there is not provision of deleting them in lump. In this post we will discuss the method which will help you to delete the messages one by one.
Open the application and then enter the chat thread, and then tap and hold any of the single chat sent to you. If you will just tap the chat then you will be directed to another page where you will see the detailed information about that chat message which may include the location from which it was sent and the medium which was used to send it. So, tap and hold for the correct options, you will see delete option popped up, it is like copy and paste option which are usually popped up when we tap and hold any text on the webpage or in any other application.
It will ask the confirmation as this step cannot not be undone again.
This way you can delete a single message from the chat thread but it will not go away as soon as you delete it will be there unless and until you refresh the messenger app. The same steps can be performed when you intend to do the same with Facebook main application. We will try to find a tweak which can help you to delete all the threads from the messenger application.