Nyctixalus pictus — Cinnamon Frog
Some other names for this species:
Painted Indonesian Treefrog, Spotted Treefrog, White-spotted Treefrog, Cinnamon Treefrog, White-spotted Brown Frog
This species has been classified as Ixalus pictus, Rhacophorus anodon, Philautus pictus, Philautus anodon, Rhacophorus pictus, Hazelia picta, Hazelia anodon, Nyctixalus anodon, Edwardtayloria picta, and Theloderma pictum, in addition to its current classification. We'll see how long this one lasts.
When I saw one of these hopping across the trail on my first night in Malaysia, I immediately realized that I didn't know what it was, and also that I had quite definitely not seen one before.
These frogs breed in water-filled tree holes My guide Kurt "Orion" G led me straight to this one, which was hanging out by one of these holes.
I wonder what is the evolutionary advantage of this color and pattern in the rainforest. The frogs draw my attention, which certainly doesn't help them, but perhaps to the eyes of their predators these frogs blend in somehow. Many brightly-colored frogs are toxic to predators, but I haven't found any mention of toxicity for these frogs.
On my return visit to Malaysia the following year, I was familiar enough with the local frog fauna to know what this was at first glance.
A Field Guide to the Frogs of Borneo tells me that this species is widespread across Borneo. In my limited experience it doesn't seem to be particularly abundant anywhere though; I saw two at the same tree hole last year, but otherwise I've never seen more than one in any evening.