Heat oil in a deep pot. Add spices (A), (B) and (C). Fry until fragrant and oil rises.
Add chicken and 1 cup thin coconut milk. Cook to the boil. Reduce the heat and simmer for a while. Add thin coconut milk gradually.
Add potatoes and tomatoes; cover and continue to cook until meat is tender.
Pour in thick coconut milk and adjust with seasoning to mix. Bring to a boil until oil rises. Serve curry with the steamed turmeric rice.