Complex sentence: Entering their territory, he laid siege to the capital Ayutthaya but he was badly injured when a cannon he was watching being loaded burst, prompting a hasty retreat of the Burmese, and he died of his wounds before they reached the River Salween.
Split into simpler sentences: Entering their territory, he laid siege to the capital Ayutthaya but he was badly injured when a cannon he was watching being loaded burst, prompting a hasty retreat of the Burmese. Alaungpaya died of his wounds before they reached the River Salween.