Combine soy sauce, lime juice, garlic, ginger and chilli flakes in small bowl. Reserve 3 tablespoons of this mixture; cover and refrigerate. Add water to remaining mixture. Pour over duck; toss to coat. Cover and refrigerate at least 30 minutes or up to 2 hours, stirring mixture occasionally.
Soak 8 bamboo skewers for 20 minutes in cold water to prevent them from burning; drain.
For the peanut sauce: combine coconut milk, palm sugar, 3 tablespoons reserved soy sauce mixture and peanut butter in a small saucepan. Bring to a boil over medium-high heat, stirring constantly. Reduce heat and simmer, uncovered, 2-4 minutes or until sauce thickens. Add crushed peanuts and coriander.
Drain duck; reserve marinade. Weave 2 to 3 duck strips accordion-style onto each skewer. Brush duck with reserved marinade. Discard remaining marinade.
Grill skewers under grill until duck is no longer pink, turning halfway through grilling time.
Serve with warm peanut sauce for dipping.