It looks very similar to some Ternstroemia (Ternstroemiaceae- Pentaphylacaceae s.l.) fruits. Could you provide photos of leaves or another plant´s part?. The fruits of Ternstroemia I know, however, have seeds with red arils and pericarps not so red,
I agree with Anshary, the plant is a cucurbit (Bali Melon) and belongs to the genus Trichosanthes.
"This fruit is found dangling in the lowland forests of Bali. From a distance, the plant resembles a Passiflora, with similar leaves, but upon closer inspection it clearly turns out to be a cucurbit. The fruits are ribbed, ovoid cylindrical and ripen a brilliant crimson red. They last for a very long time and are very showy, and even though they are probably not edible, the plant has potential as an ornamental for the tropical garden. The fruit would perhaps also make a beautiful additions to floral arrangements."
http://www.rarepalmseeds.com/pix/TriMel.shtml
However, to identify the plant to the species level, you need to provide some more info about its morpho-pomological characteristics.
Thank you very much Mr Anshary and Prof. Shtayeh for your valuable answers. they are really very helpful, I checked the link and it looks very similar.
Family I have no idea, but the monkeys and birds know their business. The red must be warning coloration. At least I wouldn't eat them before anyone else.
I agree that it is a Trichosanthes (Fam. Curcubitaceae). Some species of this genus are very appreciate in traditional medicine, but other are well known due to their high toxicity. If you have a picture of the leaves and flower, it is posible to identify the specie (maybe ....Trichosanthes tricuspidata? T. cucumeroides?)
Genus: Trichosanthes (Faily: Cucurbitaceae). Specie (sp): For a cplmplete taxonomic classification it is necessary to have some more specific phenological and geobotanical characteristics. (Could be T. cucumeria L.?)