DaCook, here's a picture of this fruit. It's called Chompooh locally and Rose Apple in the supermarket labels. Apparently its official name in the books is Java Apple. To give you an idea of it's size, it's height is the same as that of a regular apple.
The texture when you bite into it is almost like that of an apple too, but the meat is less dense and more watery with a sweetish taste. Overall a very refreshing fruit to munch on.
This is also available in the Philippines (called Macopa) but I don't know anyone who would actually buy it to eat it. That's because macopa in the Philippines has asolutely no sweet taste, just a watery even slightly sour taste. Maybe if one had a macopa tree one would eat the fruit to avoid waste.
The Thai rose apple is definitely much better tasting and is actually a popular fruit.