Fill large roasting pan half full of water; set aside.
Gently pull back husks from corn, and remove silks but not husks.
Place corn in a roasting pan, and add more water until corn is covered. Soak corn for 4 hours and up to overnight.
PREP GRILL AND CORN:
15 minutes before smoking, prepare your smoker by adding soaked wood chips or pellets, and preheat to 225 degrees F.
Remove corn from water and place it on paper towels to dry.
In a small bowl, whisk together butter, brown sugar, paprika, onion powder, garlic powder, and salt. Brush corn with butter mixture, and sprinkle with green onions.
SMOKE CORN:
Gently pull husks back over corn. Smoke for 60 minutes, turning once with long grilling tongs during smoking. Let the corn sit for 10 minutes.
SERVE:
Pull husks back and serve. Garnish with sliced green onion if desired.