Cover the dried chiles with boiling water and soak for 15 minutes. Drain.

Blend the softened chiles, shallots, garlic, lemongrass, shrimp paste, 2 tablespoons oil, and 2 tablespoons water into a paste.

Heat the remaining 2 tablespoons oil in a skillet over medium heat. Add the chile paste and cook for 8–10 minutes, stirring frequently, until darkened and fragrant. Stir in the tamarind, brown sugar, and salt. Add a little water if it becomes too thick. Remove from the heat.

Pat the stingray dry. Rub with lime juice and salt, then coat both sides with the sambal. Reserve a little sambal for serving only if it has not touched raw seafood.

Heat a gas or charcoal grill to medium-high, about 400–425°F. Clean and oil the grates. Rinse the banana leaves and briefly warm them over the grill until pliable.

Place the stingray portions on banana leaves or heavy-duty foil. Grill with the lid closed for 5–7 minutes per side, depending on thickness. The flesh should be opaque and separate easily from the cartilage, reaching 145°F internally.

Rest for 2–3 minutes. Serve hot with lime wedges, cucumber, red onion, and additional cooked sambal.

Replace the homemade sambal with about ¾ cup prepared sambal oelek, mixed with 1 tablespoon brown sugar, 1 tablespoon tamarind concentrate, and 1 teaspoon shrimp paste.