Is anyone familiar with that island. Is it within eyesight of Hua Hin central?
I'm thinking what is the snakes main diet on there, unless the rodent population is kept in balance with the snake population. I wouldn't think there is enough sea bird nesting to keep them supplied with eggs/chicks.
Take a look at the link. Several other snake species use tail vibration as a warning/defense it appears.
https://en.wikipedia.org/wiki/Tail_vibration