Q:

wordpress str_replace the content with tag

it is possible to find tag in the content and replace with link? 
function replace_content($content){
  foreach(get_the_tags() as $tag) {
    $out .= $tag->name .','; 
    $csv_tags .= '"<a href="/' .  $tag->slug . '" >' .  $tag->name . ' </a>"';
  }
  $find  = array($out);
  $replace = array($csv_tags);
  $content = str_replace($find, $replace, $content);
  return $content;
}
add_filter('the_content', 'replace_content');

A:

I can see that you are constructing an array with only one element, something like this:
array( 'green, yellow, red' )

instead of an array with multiple elements:
array( 'green', 'yellow', 'red' )

Try to replace these lines:
$out .= $tag->name .',';  
$csv_tags .= '"<a href="/' .  $tag->slug . '" >' .  $tag->name . ' </a>"';

with 
$find[] = $tag->name;
$replace[] = '<a href="/' .  $tag->slug . '" >' .  $tag->name . ' </a>';

and remember to declare the arrays at the top:
$find = array();
$replace = array();

