We can suspend a parked domain using Rewrite rule in .htaccess while keeping the main domain intact.
In .htaccess file, add the following.
RewriteCond %{HTTP_HOST} ^parkdomian.org$ [OR]
RewriteCond %{HTTP_HOST} ^www.parkdomian.org$
RewriteRule ^(.*)$ http://x.x.x.x/suspend.txt [R=301,L]
where x.x.x.x is the server IP.