Oh ok! I understand now. In order to Thanks the poster for his post. Just look under the poster's username, and you will find STARS. You can thanks the poster by clicking on the stars. When you see the "Check" mark, that means you have thanked the poster. It a great job for anyone who want to rate a poster.
But that is not really the Thank MOD that I am looking for, and I think that is not the one that most member are looking for.
What I, and other, are looking is a Button (just like Reply or New Topic), and when you click on it, at the end of the first post, it will appears the username of the person who thanked the post. So, when we enter, we can see the list of all username that have thanked the post. So the poster will find himself happy that many members thanked him.
Also, below the avatar, and the whole bunch of description such as Gender, Location.. we should see the number of Thanked that this member have made, and have received.
That will be the best THank mod that we are looking for.