Redirect To www from non www site for subfolder using .htaccess

I want to redirect from http://domain.com/folder/ to http://www.domain.com/folder/

I have tried below code

RewriteCond %{HTTP_HOST} ^domain.com [nc]
RewriteRule ^(.*)$ http://www.domain.com/$1 [r=301,nc]

AND

RewriteCond %{HTTP_HOST} domain.com [NC]
RewriteRule ^(.*)$ http://www.domain.com/folder/index.html [R=301,NC]

It redirects to http://domain.com/ to http://www.domain.com/
Not http://domain.com/folder/ to http://www.domain.com/folder/

also it redirect to http://domain.com/folder/ to http://www.domain.com/

But not to http://www.domain.com/folder/

Please suggest what issue and help to solve it.
Thanks.