there were some attempts to include multithreading into standard ml. john reppy's manticore project came quite far but wasn't fully implemented.
currently mythryl, a sml/nj derivative with c-flavored syntax, is about to get a full multithreading support. check out mythryl.org and the status updates on the mailing list.
These features are /somewhat/ available as 3rd party libs (OCaml), but you won't see GHC or Erlang-style thread use.