Tropical Zone Gardening: A fruit in Thailand, 1 by pp888

pp888 wrote:
Hi,
From the plant I am looking for I know only the fruits (see the middle of the picture). The fruits are smaller and a little bit slimmer than apples. The end where the flower has been is round (like a tomato). The fruit inside has a consistence like a firm pear. The flavor is fresh and sweet like an apple or a pear. In the middle there is no stone but a kind of small carpel which I unfortunately did not examine further.

As I was told by a Thai woman the name should be "phut saa". When looking up this name in Google I found only the translation "jujube" (Ziziphus spec.). Both species of that genus I know of (Chinese Jujube, Z. jujuba, and Indian Jujube, Z. mauritiana) have fruits which are very different from the fruits I have photographed and eaten.

The fruits have been sold in november in many places in the north-east part of Thailand. Can anybody help me?