Complex sentence: Bengkalis Regency comprises the whole of Bengkalis Island which is located in the Straits of Malacca, together with a wide swathe of the eastern coastal area of Sumatra Island as well as other islands (such as Ripat Island) within the archipelago to its northeast.
Split into simpler sentences: Bengkalis Regency comprises the whole Bengkalis Island which is located in the Straits of Malacca. The area covers of eastern coastal area of Sumatra island as well as part of the archipelago to its northeast.