Preheat the oven to 400 degrees F and lower the rack to the lowest position.
Dry the turkey thoroughly with paper towels. Stuff the basil, lemongrass, scallions and ginger slices in the main cavity and smaller neck cavity. Close the neck cavity with a toothpick. Most turkeys come with the drumstick tucked under a flap of skin to keep them secure. If your's didn't, tie the legs together with kitchen twine.
Mix the mayonnaise, sriracha, ginger powder and garlic powder in a bowl. Massage over the entire bird, leaving 2 tablespoons of mayo mix for later. Then salt and pepper liberally.
Place the turkey, breast side down, in a roasting pan on a rack. Pour two cups of water in the pan and place in the oven.
Roast for 1 hour. Using paper towels or turkey lifting forks, carefully flip the bird breast side up. Rub the remaining mayo mixture over the top. Add additional water to the pan if needed, and roast another 45-60 minutes. You want to interior temperature of the bird to reach 165 degree F in the thigh area. *If the turkey starts getting too dark on top, cover it loosely with foil. Allow the turkey to rest at least 20 minutes before slicing.