Trimeresurus sabahi Sabah Pit Viper
Some other names for this species:
Sabah Bamboo Pit Viper
Some authorities place this species in the genus Popeia.
Subspecies I've seen:
T. s. fucatus
Siamese Peninsula Pit Viper
T. s. sabahi
Sabah Pit Viper
Trimeresurus sabahi fucatus Siamese Peninsula Pit Viper
Bukit Fraser, Pahang, MalaysiaJanuary 19, 2017
Siamese Peninsula Pit Viper (Trimeresurus sabahi fucatus) Siamese Peninsula Pit Viper (Trimeresurus sabahi fucatus)
Trimeresurus sabahi fucatus is the more widespread low-altitude version of Trimeresurus nebularis. However, both types are reported to exist on Bukit Fraser (aka Fraser's Hill), and the references that explain how to distinguish them disagree with and contradict each other. So let's just say that each of these snakes, which were found within ten feet of each other, is definitely one or the other.

The red-and-white stripes separating the sides from the bottom visible in the first snake seem to generally be considered conclusive evidence for T. sabahi fucatus, and perhaps evidence that it's a male (though maybe females have these stripes in some populations, according to some authorities).

The sharp delineation between the reddish top-of-tail and green bottom-of-tail in the second snake are often cited as evidence in favor of T. nebularis. But it seems quite surprising that the two nearly-identical species would be found within ten feet of the other (you'd expect selection pressures to have favored one or the other). And also, the second snake's eyes are definitely more yellow than green, which seems to rule out T. nebularis. So I'm just going to call them both T. sabahi fucatus.

My Travelogues and Trip Lists page includes a complete list of the herps I saw in the wild on this trip to Malaysia, as well as a travelogue of the trip.

Bukit Fraser, Pahang, MalaysiaJanuary 20, 2017
Siamese Peninsula Pit Viper (Trimeresurus sabahi fucatus)
This one also has the sharp delineation between reddish top-of-tail and green bottom-of-tail, so perhaps it is T. nebularis. But if it's T. nebularis, then that second snake above should also be T. nebularis, and I called that one T. sabahi fucatus because the first one seems to definitely be T. sabahi fucatus.

But also, some references claim that T. sabahi fucatus has more of a matte finish when photographed with a flash, whereas T. nebularis has more of a glossy finish. This snake looks pretty glossy to me (based on the extra-shiny flash highlights). On the other hand, it was a very wet night so maybe the snake is extra reflective just because it's wet. I'm soooo confused!

Trimeresurus sabahi sabahi Sabah Pit Viper
Park headquarters area, Kinabalu Park, Sabah, MalaysiaMarch 4, 2018
Sabah Pit Viper (Trimeresurus sabahi sabahi) Sabah Pit Viper (Trimeresurus sabahi sabahi)
Trimeresurus sabahi was originally restricted to Mt. Kinabalu and some nearby high elevation areas. Later some other green tree vipers from various areas outside of Sabah were lumped in as subspecies, so now neither the standard English name nor the scientific name make sense.
Park headquarters area, Kinabalu Park, Sabah, MalaysiaMarch 5, 2018
Sabah Pit Viper (Trimeresurus sabahi sabahi)
This was a cute li'l baby snake, trying so very hard to look scary.
Online references:
Printed references: