It's not recommended. It's like re-freezing chicken once it's set out on the counter all day. Not something I would want to eat.. Ick. They are much more likely to burst if you refreeze.

How old is the snake? If he/she is a hatchling, then I would try feeding live for the first couple of feedings, just until he gets happy and consistent about eating. Then you can try and switch to f/t. They don't readily take f/t when young, as they don't recognize it as prey yet.