"If you want a Robinson Crusoe holiday, Head Tien is as good as it gets if you still want an ensuite, a restaurant and a pool. Utterly charming place, could do a bit more on maintenance, cleanliness & shuttle options for the price, but the staff and location make up for any gaps.
The snorkling is also great - shoals of large parrot fish chopping on coral.
Be aware that it is on an almost vertical hill, so lots of steps up to rooms and down to restaurants so if you're not fit, it might not be...