Sorry, don't have a photo. My stepson saw it in the garden. Plenty of ground cover around now and still very dry. We live in a farming area near Nakhon Sawan. This one was about 5' long. He describes it as thick and very black, he says the head was not large. Apparently not aggressive as it quickly made an exit. We don't get many snakes apart from the odd python or rat snake as the garden is walled. But this is the time of year for them and I know there are a few cobras in the forest next door. I keep well away from there.. So possible ID's would be much appreciated

Well...without a photo ....and per your description....it could be a 5 foot long thick black snake with a small head. But... taking a really Wild Ass Guess it could be of the Asian Pipe Snake species. That comes closest to your description. It didn't have a red tip on it's tail did it? Without any more information or a photo I'll stick to my first guess.

Edited April 18, 201412 yr by Mrjlh

You can browse through these images and see if you find a match - Black snakes thailand

Thanks guys. Problem solved - I hope. After further questions and a look at the snake pics, my son has changed his mind and now thinks it was a rat snake - much to my relief. This is consistent with our previous visitors, but glad it wasn't a cobra.