htaccess redirect domain to subdirectory without changing URL

.htaccess redirect domain to subdirectory without changing URL

You can use this rule:

RewriteCond %{HTTP_HOST} ^(www\.)?domain3\.in$ 
[NC]RewriteRule !^subdir/ /subdir%{REQUEST_URI} [L,NC]

This will prefix every request for domain3.in with /subdir if it is not already there.