If he is smart, you should be proud and happy, and not worried about developing it further. I am all for stimulation of mind by generating curiosity, interest, passion, inclination. But I am not much in favor of training tender minds without having the need to do so. I have seen anxious parents putting pressure and thus robbing off the naturally present smartness.
You may do a lot of creative activities with him. Talking helps a lot develop their skills in general. Check this for more ideas http://learningstations.blogspot.in/2013/02/play-ideas-for-tiny-tots.html
I need more info on RBT...is there any coaching in Mumbai for this?