If the 3rd supralabial scales are large and touching the eye and nasal shield, the snake may be
If the head scales are large, it may be poisonous or non poisonous. Look for the 3rd supra labial and if it is touching the eye and the nasal shield, it is poisonous (cobra or coral snake) Ref: FORENSIC MEDICINE AND TOXICOLOGY Dr PC IGNATIUS THIRD EDITION PAGE 511
Krait
Pit viper
Saw scaled viper
Cobra
Poisoning