Peel and devein the shrimp. Wash thoroughly under running water. Drain in a colander for 15 minutes. Sprinkle with 1teaspoon of the salt and set aside for 10 minutes.
Place a medium nonstick sauté pan over medium heat. Add the cumin, coriander, and dried chiles, and dry-roast for 5 to 8 minutes. Transfer to a bowl and set aside to cool.
Put the roasted spices, the coconut, ginger, garlic, tamarind pulp, and 1cup (200ml) water in a mini food processor, and process to a fine paste.
Place a medium nonstick sauté pan over high heat and add the oil. When small bubbles appear at the bottom of the pan, lower the heat to medium, add the onion, and sauté until golden brown. Add the green chiles and the remaining ½teaspoon salt and sauté over medium heat for 3 minutes more, stirring continuously.
Add the ground paste and 1½cups (300ml) water. Bring to a boil, then lower the heat to low and add the shrimp. Cook for about 5 minutes or until the shrimp are cooked through.
Stir in the vinegar. Transfer to a serving bowl and serve hot.