Is there ak-47 on thing thin arena 2

Depends on what you mean. A synthetic AK-47 with a foldable stock is seen in the intro, but it's not used anywhere else in the game. A similar AK-47 is usable in Thing-Thing 4, based upon the model in Arena 2's intro, though the design is different, with a shorter and more detailed stock, a bit more detail in the reciever, a shorter barrel, a strangely positioned and angled grip and a blockier magazine which seems to have less quality.