How to allow internal links using wp_kses filtration

I’m working on front end submission and of course I want to secure data by filtering before inserting to database.

The form contains repeatable fields group data which I want filter by wp_kses function (external urls, etc.) but it would be great if user will be able to insert internal link to another publication and wp_kses will pass it..

I’ve managed this way:

$r_step_description = $_POST['step_description'];
            $allowed_html = array(
            'br' => array(),
            'em' => array(),
            'strong' => array(),
            'p' => array(),
            'br' => array()
        );
        $allowed_a = array(
            'a' => array(
                'href' => true
            ));
    for ($i = 0; $i < $count; $i++) {
        $domain = strpos($recipe_step_description[$i],'site-name.com');

    if(!empty($domain)){
             $allowed_html = array_merge($allowed_html, $allowed_a);}
             $r_steps['steps']['text'][$i] .= wp_kses(wpautop($r_step_description[$i]),$allowed_html);
        }

Everything ok with this except one thing. When second link to external domain is present – this link will be unfiltered.

Any clue?

Thank you in advance!