How to copy a forum thread?
You can try using Bundle Copy Module...


  Has export/import support for:
  
  
  Node types
  Taxonomy
  User
  Field API fields
  Field groups
  
  
  You can find the export/import links for the supported entities on
  following paths:
  
  
  Nodes: admin/structure/types
  Taxonomy: admin/structure/taxonomy
  Users: admin/config/people/accounts