I was visiting one of my brother-in-laws in a village some 20km to the east of Udon Thani where he has a small fish rearing farm with the intention of doing a spot of fishing. The pond contains approximately 5000 small Catfish that he feeds for up to four months, then sells them on to a fish supplier for the local markets.
Being the curious ferang I just had to pick it up for a closer inspection but as soon as I did that, the "caterpillar" retreated back in to its DIY shelter. I placed it back on the floor and waited for it to emerge once again, this time with the camera to hand.
I have recently been advised that this "Caterpillar" is actually the larva of a caddisfly. (see the comment to this post below) I really should have seen that a lot earlier but it has been many years since I last saw one that it completely slipped my mind.