Preheat the oven to 375 degrees.
In a large mixing bowl, whisk together the peanut butter, fish sauce, tamari, vinegar, lime juice, and maple syrup. Add the coconut milk and water and continue whisking until well-combined. Fold in the white and light green scallions, ginger, chile (if using), rice, and sea salt. Transfer the whole mixture to a large (10-inch) oven-proof skillet or 9 x 13 baking dish.
Make the chicken: To the same mixing bowl (it’s fine if some casserole mixture remains), combine the chicken, ground turmeric, ground coriander, ground ginger, salt, sriracha, oil and lime juice. Arrange the chicken on top of the peanut butter rice mixture in the skillet or baking dish.
Bake the casserole for 45 minutes, or until the rice is tender and most of the liquid is absorbed. Remove from the oven and allow to rest for 5 minutes. Garnish with the sliced cucumbers and green scallions.