Do check out siam square!! I wish i could visit bkk. There is also a water park too!!

You should visit the temples for sure (wat phra kaew wat po, what arun and so on) and I would never eat in a restaurant when I go back home! Street food is the best there is and restaurant food is just... ugh >.> Of course, not all are bad but street food is still the best.
Also, make a boat tour where you can visit most of the temples and the royal palace and maybe the sky bar, even though the prices there are a bit expensive. Lumphini Park, the Chatuchak Park or the other parks are worth a visit as well.