Ptyas mucosa

English name: Oriental Rat Snake
Scientific name: Ptyas mucosa (formerly Ptyas mucosus)
Thai name: Ngu Sing Hang Lai, Ngu Sing Dong

Description: To 370cm long. The largest snake in Bangkok other than the pythons. Eyes are notably large. Tail is especially long. Body is light brown to black above with narrow black crossbands on the last third of the body that become more indistinct with age. Juveniles are olive and usually have light crossbands on the front two-thirds of the body. Underbelly is grayish white to yellow with thin black banding.

Similar Species: Indo-Chinese Rat Snake lacks the black crossbands on the last third of its body.
Monacled Cobra has smaller eyes, a blunter head, and a characteristic marking on the back of the neck/head that expands when displaying.
Yellow-spotted Keelback has black markings on the entire body.

Habitat: Can be found in almost any habitat from thick jungle to agricultural fields and parks. Appears to prefer open woodland, scrubland, lightly treed grassland, and parks, possibly tending towards drier landscapes than the Indo-Chinese Rat Snake. Spends most of its time on the ground but climbs well and will often sleep in trees. Will enter human dwellings while hunting rats.

Place in the ecosystem: Primarily preys on rats and helps control rodent populations in Bangkok. Will also feed on squirrels, bats, frogs, lizards, smaller snakes, birds, and even turtles. Its juveniles provide food for larger snakes, monitors and birds of prey.

Danger to humans: This large snake becomes aggressive and strikes repeatedly when cornered, potentially drawing blood. However, it is non-venomous and cannot cause any serious injury.

Conservation status and threats: The Oriental Rat Snake has no known conservation issues in Thailand, but is hunted for its meat. Is listed as Endangered in China. In Indonesia, TRAFFIC has raised official concerns due to the large numbers of Oriental Rat Snakes that are exported out of the country outside of official government regulation.

Interesting facts: When threatened this snake will sometimes inflate its neck and make a growling noise. Some herpetologists believe this is mimicry of the King Cobra, a similarly large southeast Asian snake with an extremely venomous bite. Unfortunately, the attempted mimicry may be counterproductive when done towards humans, as anything thought to be a cobra is likely to be killed.

After capturing a potential prey item, the Oriental Rat Snake will use its body to press the animal against the ground or another hard surface until it suffocates, rather than using its coils to wrap around the food like many other snakes.

References:
Snakes of Taiwan: Ptyas mucosa
University of Hong Kong: Ptyas mucosus
Wikipedia: Ptyas mucosus
Wildlife Watch: Future of Asian snakes at state
A Photographic Guide to Snakes and Other Reptiles of Peninsular Malaysia, Singapore and Thailand
A Field Guide to the Reptiles of South-East Asia