Polehawk, you are right, it was Lycodon laoensis- completely harmless (besides the tiny pin pricks the teeth could make in a bite
Jungle Dave, the Red-Necked Keelbacks (Rhabdophis subminiatus) do have a dangerous bite, but is one to bite out of defense, not out of aggression; it will always go away when given the chance.
Fussychunk, that appears to be Ptyas korros (Indochinese Rat Snake). They are rear fanged, but should be considered harmless. Their venom is only capable of producing minor swelling. Many Thais love to eat them. Care should be taken, since the pattern on them is similar to some King Cobra (Ophiophagus hannah) variants; some have similar banding, like the one in the picture, or outlining of the scales.
Benzman, your snake is a Xenochrophis flavipunctatus. This is actually what your earlier snake was, which is almost identical to Xenochrophis piscator. I had missed a small pattern characteristic in the picture on your post of 7 April, which was much more clear in this picture. The two species are very difficult to tell apart and I have seen some of the better references misidentify the two in pictures (not sure whether it was the author's mistake or the publisher's). Both are rear fanged and should be considered harmless.
On the subject of spiders, scorpions and centipedes, none of the spiders appear here in Thailand to be really dangerous, I have been told by one of the biologists that I work with that the smaller brown scorpion can cause some ill effects and of course, the centipede can cause some ill effects. My wife (while in bed) and I (one hiding in my trouser leg) have been stung over the past month by the smaller brown scorpion and besides quite a bit of pain, we did not suffer any ill effects.













