In a food processor puree 6 green chilies, shrimp paste, lemon grass, galanga root, lime zest, cilantro leaves, shallots, garlic, salt, cinnamon and cilantro root. In a Dutch oven heat oil and saute paste over medium heat for 3 minutes. Add chicken thighs and turn to coat. Turn heat to high, add water and bring to a boil. Reduce heat to medium, cover and simmer 1 hour. Remove chicken and reserve. Chill liquid until it congeals.
Degrease chilled liquid. Reheat gently. There should be 1 cup of liquid -- add water if needed. Dissolve tamarind concentrate in 2 tablespoons of hot water and add. Add fish sauce. Bring to a boil and thicken with cornstarch mixed with a little water. Turn heat to very low and add coconut milk, the reserved chicken thighs, cut in half, and simmer 15 minutes. Add remaining green chilies and tomatoes. Simmer gently for 15 minutes more. If sauce is too thick, thin with a little coconut milk just before serving. Sprinkle wit