In a large bowl, combine the soy sauce and the fish sauce, then add in the shrimp. Cover the bowl and allow to marinate, in the refrigerator, while preparing sweet potatoes.
Peel and grate sweet potatoes. With hands, squeeze excess moisture from potato if necessary. In a large bowl, combine the sweet potatoes and the remaining ingredients, except the flour, mixing well. Stir in the flour and mix to combine.
Remove the shrimp from the marinade to a cutting board, then chop and fold into the sweet potato mixture.
In a large heavy bottomed skillet, over medium-high heat, add 2 tablespoons of the peanut oil. Form cakes, as flat as possible and carefully add first batch to pan. Fry for 1 1/2 to 2 minutes on the first side and 1 minute on the second side. Remove to a serving platter and season with salt. Add remaining oil to the pan and cook the second batch. Serve immediately.