WordPress in subfolder dont work

Your .htaccess looks just fine, but you need to tell WordPress itself that it got moved. Simply put the following line into your wp-config.php, then access your site’s login page under the new URL and login. After that you can remove this line.:

define('RELOCATE', TRUE);

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Alternatively add the following two lines to your wp-config.php, then navigate through the site a few pages far, then you can remove these lines.

define('WP_HOME', 'http://domain.com/blog');
define('WP_SITEURL', 'http://domain.com/blog');

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Source: Changing The Site URL.