Place a dry wok or 14-inch (35cm) skillet over medium-low heat, add the galangal, and toast, stirring constantly, until dry to the touch and fragrant, which should take about 1 minute. Transfer to a bowl.
Add the shallots, chile powder, fish sauce, and lime juice to the bowl with the galangal, stir to mix, and set aside.
Return the pan to medium heat. When the pan is hot, add the chicken and water and cook, stirring and breaking up the meat with the edge of the spatula, just until the chicken is cooked through, about 5 to 8 minutes. Transfer the chicken and its juices to the bowl with the dressing.
Stir everything together well, then taste to see if the seasoning needs correcting. The salad should be predominantly sour, then salty. Adjust the seasoning as needed. When the salad tastes right, stir in the rice powder, sawtooth coriander, and mint. Serve immediately with the cabbage on the side.