Hypsiscopus plumbea

Yellow-bellied Water Snake Rice Paddy Snake Hypsiscopus plumbea Enhydris plumbea งูปลิง thailand
Yellow-bellied Water Snake Rice in Phayao (Jon Hakim / CC BY-NC-SA)

English name: Yellow-bellied Water Snake (aka: “Plumbeous Water Snake” or “Rice Paddy Snake”)
Scientific name: Hypsiscopus plumbea (formerly Enhydris plumbea)
Thai name: งูปลิง (Ngu Pling)

Description: To 77cm long. This small water snake has a moderately broad head with nasal scales in contact. It is uniformly olive, gray, or black above with smooth scales in 19 rows at midbody. Some specimens from other countries show faint dotted or netlike patterns. Belly is pale cream to yellow.

Similar Species: Glossy Marsh Snake never has a yellow belly, has 17 midbody scale rows, has its nasal scales separated by an internasal, and is restricted to coastlines near marine environments.
Rainbow Water Snake has a smaller head and two colored lines down its sides.
Sunbeam Snake is iridescent, has a narrow wedge-shaped head, and is whitish-gray on the bottom.
Red-tailed Pipe Snake has a small head and a barred underbelly.
Yellow-striped Caecilian lacks scales, has yellow stripes on the side rather than a yellow belly, and has a distinctly non-snake-like head.

Range: Found from Burma east through southern China and Taiwan and south south through southeast Asia across nearly all of Indonesia.

Habitat: Slow-moving rivers, ponds, swamps, rice paddies, flooded meadows, and other wetland habitats with stagnant water. Forages from dusk until dawn. Found on land more often than other water snakes, but rarely far from the water.

Place in the ecosystem: Feeds on fish, frogs and tadpoles. Eaten by larger snakes, large fish, monitors, civets, and wading birds.

Danger to humans: The Yellow-bellied Water Snake will aggressively strike when cornered on land, but its small size keeps it from being able to inflict much damage. While it is a rear-fanged snake with some venom, the venom has a limited effect on humans, possibly leading to some swelling in the worst cases.

Conservation status and threats: No known conservation issues. This is a common species in Thailand, though its population in Taiwan is endangered.

Interesting facts: Yellow-bellied Water Snakes are excellent swimmers but move awkwardly on land. When faced with a threat on land, they will sometimes flip their bodies up into the air and backwards with a reverse-striking motion and then take off in a new direction, propelling themselves erratically towards the water.

References:
Snakes of Taiwan: Enhydris plumbea
Reptiles of Hong Kong: Enhydris plumbea
The IUCN Red List: Enhydris plumbea
A Checklist and Key to the Homalopsid Snakes
A Photographic Guide to Snakes and Other Reptiles of Peninsular Malaysia, Singapore and Thailand
A Field Guide to the Reptiles of South-East Asia
A Field Guide to the Snakes of South Vietnam