I am considering moving to the Krung Thon Buri BTS area. I know very little about this area however it seems to have a very different (positive) air about it...its quieter, by the river etc. But what is there to do on that side of the river? Shopping? Nightclubs? Things to do?

Wing Wien Yai market has good food, for nightlife & bars upscale hotels along river or short ride to Silom.

I am considering to buy a condo in this area..

So far i not saw to much, except a badminton hall. But to silom it isn't too far.

If someone know more information what exists in this area i also would be happy to know.

Not much right there.  The Mall Thapra is perhaps the closest Thon Buri shopping, and the Peninsula and the Marriott both offer upscale bars and restaurants.  Further away, there is a nice Beer Hall with entertainment near Central Rama II.

For nightlife, I don't think there is much aimed at Westerners, but as others have pointed out, Silom is not very far away.