In a medium bowl, whisk the rice flour, tapioca starch, sugar, and salt for the batter. Whisk in the coconut milk and water until smooth. Let the batter stand while you prepare the topping.
In a small bowl, whisk the coconut cream, rice flour, sugar, and salt until smooth. Stir the corn and scallions together in a separate small bowl.
Heat a khanom krok pan, takoyaki pan, or other shallow well pan over medium-low heat. Brush each well lightly with oil. The pan is ready when a small drop of batter sizzles gently rather than browns immediately.
Whisk the batter again, then fill each well about two-thirds full. Cover the pan and cook until the batter begins to look set around the edges and bottom.
Stir the coconut topping and spoon a small amount over each pancake. Sprinkle with a few corn kernels and, if using, scallions. Cover again and cook until the topping is set and the bottoms are lightly golden.
Use a small spoon or thin skewer to loosen the pancakes. Traditionally, two pancakes are gently pressed together with their creamy sides facing inward. Serve warm, with the crisp sides on the outside.