If you have a function to make the AI "think", just execute it after some time. You can use the
Timer node for this.
If the AI has to do several actions, you can make it so your "think()" function returns a list of actions, then you execute them one by one with a delay between them with the timer. This way, the player will be able to see what the AI does.
If you need to modify the terrain between actions, you have two options:
1) split your think() function with delays
2) have a copied representation of the game in the AI's mind so it can make future hypothesis without messing with the current board.