.htaccess subdomain slash at end..

Sorry if this is wrong place, I did not see anything else.

So I have this on the .htaccess:

RewriteEngine On

RewriteCond %{HTTP_HOST} ^(www\.)?sub\.site\.net

RewriteCond $1 !^sub/

RewriteRule ^(.*)$ sub/$1 [L]

It works very well, except when you type in url eg. sub.site.net/folder

Then it will change the url to sub.site.net/sub/folder

But it works fine if you type sub.site.net/folder/

You can see the trailing slash on end.

Is there any solutions for this?