Coelognathus radiatus
Hong Kong (© Daniel Rosenberg) 
Hong Kong (© Daniel Rosenberg) 
Vietnam (© Scott Trageser) 
Phra Khanong (Jon Hakim / CC BY-NC)
English name: Copperhead Rat Snake (aka “Radiated Rat Snake”, “Copperhead Racer”, “Copperhead Trinket Snake”)
Scientific name: Coelognathus radiatus (formerly Elaphe radiata)
Thai name: งูทางมะพร้าว (Ngu Taang Mapao)
Description: To 230 cm long. One of the larger snakes in Bangkok. Body light brown in the front, fading to a yellowish or orangish tan toward the back of the body. Two prominent black stripes run down the first half of each side of the body. Three black lines radiate back from the eye, two slanting downwards and the other running up until it hits a black collar at the back of the head.
Relevant scale counts: 19 rows of midbody scales.
Similar Species: Asian Rat Snakes (Ptyas korros and Ptyas mucosus) lack the black stripes on the front half of the body and the unique markings on the head.
Painted Bronzeback has a yellow-to-cream stripe on its body and lacks the markings on the head.
Monocled Cobra lacks the striping on the front half o the body and lacks the markings around the eye.
Range: From northeast India through Bangladesh, Myanmar and southern China into southeast Asia to Malaysia and Indonesia.
Habitat: Prefers open grassland and shrubland, but is also found in forests and agricultural habitats. Can be found in urban areas, even where there is only a small pocket of natural habitat.
Place in the ecosystem: The Copperhead Rat Snake feeds on rats and mice and helps control Bangkok’s rodent populations. It also eats birds, lizards, and frogs. Juveniles of the species provide food for larger snakes, monitors, and birds of prey.
Danger to humans: This snake is aggressive when threatened and is large enough to inflict some damage with its bite. A recent study has found that it produces some venom, quite similar to the venom of cobras. However, it only produces a small amount of venom and does not have venom-injecting fangs, so effects in humans are limited to redness and mild swelling at worst.
Conservation status and threats: In Thailand this snake is common with no known conservation issues, but it is listed as Endangered on the China Red List.
Interesting facts: The Copperhead Rat Snake is a fast snake that will first try to flee when threatened, but when cornered will lift the first third of its body off the ground, curl its neck and body into an “S” shape, expand its neck vertically and strike aggressively with its mouth open. If that fails, it will sometimes proceeds to play dead as a last resort.
References:
University of Hong Kong: Coelognathus radiatus
Isolation of a neurotoxin (alpha-colubritoxin) from a nonvenomous colubrid
A Photographic Guide to Snakes and Other Reptiles of Peninsular Malaysia, Singapore and Thailand
A Field Guide to the Snakes of South Vietnam
Reptiles and Amphibians of Thailand 
I may be wrong, and I am looking into it, contacting as many experts as I can..but at least some sources claim this species has a mild venom.
I cannot confirm this, other than that the number of times I have been bitten by this species, I always experience swelling, where with Ptyas mucosa or korros, I do not show any swelling.
You may want to check the different sources, I would love a definitive answer.
Thank you very much for that correction. Bryan Fry says that he has isolated venom from it, so I would certainly say that it indeed has venom. In fact, the venom is rather toxic, though the snake only produces it in very small amounts. His team published a paper on it in 2003, but the general literature I had used for this entry hadn’t mentioned the discovery. I will update the entry soon.
I haven’t been bitten by this species before, so I haven’t noticed any such effects myself.
Hi Jonathan, I encountered a Copperhead Racer 3 times (I think it was the same one) at Con Dao Island Vietnam. 1) slithering at the edge of a small stream near a rice field. 2) swallowing a smaller snake near bushes at the same stream 3) lying in the rice field 15 meters from the stream. The last time I photographed its head close up before it fled for the stream. As I chased and photographed it full length and tried pinning it down gently with a stick for closer look, it turned and lunged with its upper body lifted high and its neck widened like a vertical flap. It made off into the stream. About 180 cm long. Picture at twitpic http://twitpic.com/7rvl7u
Very nice! It’s awesome to get to observe such a large snake in the wild, and I’ve personally never been lucky enough to see a snake swallowing another snake.
Although now I can say that I’ve seen it twice since I wrote that message! A Banded Krait swallowing an Indian Wolf Snake in Bangladesh and a Yuma Kingsnake swallowing a Checkered Garter Snake in California.
caught one this morning at my house, maid found it under our washing machine over a meter long,very very quick snake
I walk in the mornings and often see these snakes. Mostly they move away. However, today one turned and had a strike at me. I jumped onto the wall I was so scared. It then moved away and I followed it and then it went into a drain. I was scared as I didnt know what kind of snake it was but now I know after seeing your website – thanks
We don’t have many wild snakes here in the UK, and I’m so happy about that!
Hi. Saw a nice what I believe to be Copper head Rat snake today in Southern Thailand. Length about 1.5 meters. Was not aggressive but was wary of the dog barking at it. After clear, it went off into the bush towards a water hole. Have some pictures if anyone would like to see or add to the site.
Thanks Ray! At the moment I’m not actively adding photos to the site, but you can email me the pictures if you want me to check the identification on the snake.