The Buddha died of dysentery after eating his final meal. Specifically what that meal was is unknown, but the traditional account says it was spoiled pork. Some people (seemingly mostly Westerners who are uncomfortable with the idea of the Buddha eating meat, even though this is discussed in the Pali Canon many times) have decided that the final meal of “soft pork” was actually a type of mushroom and he died from poisoning. Regardless of what the food was, the Buddha knew that is was bad and would cause his death, so he made sure he was the only person to eat that meal.
This episode of his life is seldom depicted in Thai temple art and Wat Yang Tuang Wararam (วัดยางทวงวราราม), also known as Wat Ban Yang (วัดบ้านยาง), in Amphoe Borabue, Maha Sarakham province is the only place I can remember having seen it.