If the snake is underweight and undersized, feeding it normally could potentially shock its system and you could lose the snake. A small meal once every 7 days until the snake puts on some weight will be sufficient. I would slowly work the snake up to regular-sized meals.

If he isn't significantly underweight or undersized, you should be fine feeding normal-sized meals weekly, but slow and steady is imperative for emaciated animals. If the snake really is 2+ years old and fits in your palm, it is definitely very small, and I'd be careful with feeding.