With all due credit to all those who have written up sword & sorcery serpent people in past, here are some of the primary movers and shakers in the Forbidden Jungle:
No. Enc.: 1d8 (3d6)
Movement: 90′ (30′)
Armor Class: 5 
Hit Dice: 1
Damage: 1d6+1 or by weapon +1 (due to strength)
Hoard Class: IV (XIX)
Snake-men are an ancient race of serpent people that inhabits the heavy, trackless jungle. Whether a cursed mix of human and snake or a part of the natural world, none can say. The more advanced groups of snake-men often inhabit ruins, and relics of what appears to be a lost snake-man civilization are to be found overgrown in the depths of the jungle. Snake-men appear as scaled humanoids, about five and a half feet tall with a tail. They have the heads of snakes, flicking tongues, and clawed hands.
Snake-man claws are formidable weapons, but more civilized tribes make use of weapons and favor curved scimitars and long bows. In melee, a to-hit roll of 20 indicates that the snake-man has also bitten his opponent for an extra 1d6 damage. Some snake-men are said to be poisonous.
Snake-men can be fighters, clerics, magic-users, and thieves. Snake-man women can also be druids and illusionists.
Snake-men are susceptible to all magic which affects normal snakes. Cold does double damage to them, but they get a +1 bonus to saves vs. fire or heat.
Half-Snakes: These appear to be some sort of snake-man/human crossbreed, and might more properly be called “quarter-snakes.” They appear to be more human than snake, and 10% of them can pass for human if they avoid close inspection. They can be assassins, fighters, and thieves.
Snake-Lords: The upper nobility of the snake-men consists of 20′ long snakes with a human-ish upper torso with arms. These fearsome creatures have 4-7 hit dice, venomous bites, and an innate ability to charm person if eye contact is made with a victim. They are 80% likely to be magic-users of 4th-9th level.
Snake people are a staple in so many genres of fiction that it’s tough to nail them down. They’ve been done to death many times over and yet never grow too stale. I wanted a simple archetype snake people for the Forbidden Jungle, and I think this will do the trick.
As our campaign develops, there will no doubt be some alterations to the details. I want something 1HD as we use the mook rules allowing fighters 1 attack per level against 1HD or lower creatures. But I also want a little extra bite (pardon the pun) to differentiate them from orcs. And the fact that classed snake-men will not be uncommon, serving as leaders, spies, and assassins, means that some of the villains will be tough foes, indeed. And there will always be exceptional examples of these beings, snake-men who do not fit any molds or conform to any standard rules.