The "/forumthread" page:

Show all forum messages associated with a particular message thread.
The result is basically the same as /forumpost except that none of
the postings in the thread are selected.

Query parameters:

  name=X        REQUIRED.  The hash of any post of the thread.
  t=MODE        Display mode. MODE is 'c' for chronological or
                  'h' for hierarchical, or 'a' for automatic.