I'm trying to redirect a subdomain to a subfolder e.g. forums.domain.com to www.domain.com/forums

Note that I started the forums in the subfolder format but worried that members might mistakenly try to access the forums using the subdomain format.

RewriteCond %{HTTP_HOST} ^(www\.)?forums\.domain\.com
RewriteRule .* /forums [L]

From what I read the codes above should work through .htaccess, but do I still need to create a DNS A record to point to the IP address of the server?