1. Soak dried chilies in 1/4 cup hot water until soft, about 10 minutes. Whirl mixture in blender until smooth.
2. In a 10-inch frying pan over medium-high heat, stir bell pepper, onion, garlic, dried shrimp, and fresh chilies in salad oil until vegetables are limp, about 3 minutes.
3. Stir in dried chili mixture, tamarind concentrate, brown sugar, and salt; cook 2 to 3 more minutes.