Heat coconut milk in a saucepan over low heat until lukewarm, about 5 minutes; pour into a large glass bowl. Stir lime juice, paprika, sea salt, cayenne pepper, and red pepper flakes into milk until marinade is smooth.
Place kale into marinade and press down to ensure all leaves are covered. Cover the bowl with plastic wrap and refrigerate for 4 hours.
Preheat an outdoor grill for medium-high heat and lightly oil the grate. Remove kale from marinade and shake off excess. Discard remaining marinade.
Working in batches, grill kale leaves in a single layer until edges are slightly crispy and centers are soft, 45 to 60 seconds per side.