How to play pokemon TCG Platium Shaymin Lv X card?

Not quite. The main difference between PokeBodies and PokePowers is that, while PokePowers are generally an activated ability, PokeBodies are simply static effects. So long as Shaymin is in play, it's power is constantly in use and all of your other grass pokemon in play have an additional 40hp. The reason it says "you can't use more than 1 Thankfulness Poke-Body each turn." is to prevent you from having 4 shaymin on the field and raising your other pokemon's HP by 160. So no matter how many Shaymin you have with Thankfulness on the field, you only get the benefit from one of them.