Lovely photos! I think it is Begonia (Symbegonia) vinkii :)

Andrew many thanks.

I think it is Ruthiella sp. (Campanulaceae). There 4 endemic species in New Guinea so now I have to confirm the species.

I considered that, but it looks more Begonia to me from the photo. But you could be right. The definitive way to ID is to compare with herbaria specimens :)

Balsaminaceae may be another option

Yes it is Begonia sp. to me,

Regards

ASOK

I have looked into Begonia Herbarium specimens but nothing I found similar to the plant with inflorescence on the leaf surface but I found something on the link below:

http://plantillustrations.org/species.php?id_species=895784

It looks similar to the drawing in the link :)

Thank you Andrew.

I agree with you the specimens look similar with publication.