Thinking is a lot more than logic. Chess and coding are great but they're a tiny sliver on the spectrum of thought.

Read to them. Childrens books when young but progress as they get older.

Play with them. Let them dictate the game. Often it means just watching. Don't force your way; they'll tell you how to play.

Be there. Be aware of them. Ask what they're thinking about. When they show an interest in something, explore it with them. Show them the pieces but let them make the discoveries.

You probably know all of this but for others who may not know: Raising a smart child isn't just about exposing them to what we see as "clever" activities but really much more about being present.