Heat wok with oil. Rub tapioca slices with salt and deep fry in the hot oil until crispy and lightly brown. Drain on paper towel and let cool.
Put the chopped palm sugar, chopped chillies and water in a big pot (or use the same wok after removing the oil and cleaning it)and cook until sugar has dissolved. Add the tapioca and stir until they are well coated with the syrup. Remove from heat and let cool on a wire rack. Once cooled you can store them in an airtight container.