In a bowl, combine all the marinade ingredients except the chicken. Slice the chicken into long, thin strips, about 3 inches long by 1 inch wide, and add to marinade. Turn chicken to coat, cover and refrigerate for up to 4 hours.
Meanwhile, prepare the sauce: Bring the coconut milk to a simmer in a small saucepan. Whisk in curry paste until dissolved, about 1 to 2 minutes. Whisk in peanut butter, stock and sugar, reduce heat and cook until smooth, stirring constantly, about 5 minutes. Remove from heat and add tamarind juice and salt. Set aside to cool to room temperature.
Prepare relish: Place cucumber, shallot, and chili slices in a small bowl. Heat the vinegar, sugar and salt in a small saucepan, stirring, until mixture reaches a boil and sugar is dissolved, about 3 minutes. Remove from the heat, cool to room temperature, and then pour over cucumber mixture. Garnish with cilantro leaves and set aside.
Prepare grill and thread marinated chicken onto soaked bamboo skewers. Place on grill and cook 5 to 7 minutes, or until cooked through, turning once. Serve with peanut sauce and cucumber relish.
c.1998, M.S. Milliken & S. Feniger, all rights reserved