ok,
create a directory on your theme called ‘bbpress’
ie wp-content/%your-theme-name%/bbpress
find
wp-content/plugins/bbpress/templates/default/bbpress/content-single-forum.php
Make a copy of this file, and put in in the directory called bbpress that you created above, so you end up with
wp-content/%your-theme-name%/bbpress/content-single-forum.php
bbPress will now use this template instead of the original
then change lines
<?php if ( !bbp_is_forum_category() && bbp_has_topics() ) : ?>
<?php bbp_get_template_part( 'pagination', 'topics' ); ?>
<?php bbp_get_template_part( 'loop', 'topics' ); ?>
<?php bbp_get_template_part( 'pagination', 'topics' ); ?>
<?php bbp_get_template_part( 'form', 'topic' ); ?>
<?php elseif ( !bbp_is_forum_category() ) : ?>
<?php bbp_get_template_part( 'feedback', 'no-topics' ); ?>
<?php bbp_get_template_part( 'form', 'topic' ); ?>
<?php endif; ?>
to
<?php if ( !bbp_is_forum_category() && bbp_has_topics() ) : ?>
<?php bbp_get_template_part( 'form', 'topic' ); ?>
<?php bbp_get_template_part( 'pagination', 'topics' ); ?>
<?php bbp_get_template_part( 'loop', 'topics' ); ?>
<?php bbp_get_template_part( 'pagination', 'topics' ); ?>
<?php elseif ( !bbp_is_forum_category() ) : ?>
<?php bbp_get_template_part( 'form', 'topic' ); ?>
<?php bbp_get_template_part( 'feedback', 'no-topics' ); ?>
<?php endif; ?>
and save
that should do it