In a small bowl, combine the peanut butter, sweetened condensed milk, soy sauce, and water. It will be hard to mix at first but should get more creamy as you go.
Use a meat mallet to flatten the chicken thighs to about ½-inch thickness.
In a shallow dish, whisk the eggs, flour, salt, and 1 tablespoon of peanut butter. It should look like a smooth pancake batter. Add extra flour or water as needed.
In another shallow dish, add the panko breadcrumbs.
To dredge the chicken, dip it in the egg wash, then coat it in the breadcrumbs.
Heat about 1 inch of oil to 350°F. Fry the chicken 1 or 2 pieces at a time for 2-3 minutes on each side until golden brown. Transfer to a wire rack to drain excess oil.
Cut the chicken into slices and drizzle the peanut sauce top.