No need to spend a lot of time choosing your guesthouse, all are equal and have exactly the same price (500 THB per night and per person) for basic comfort: a room in a wooden or bamboo bungalow with mattresses on the floor and a mosquito net and a shack outside where there the bathroom is with Turkish toilet and large water brown with a small basin to shower. You will not have electricity just candles at night. But in front of the view from the balcony in front of your room you will quickly forget all these material considerations. The price of the room includes dinner and breakfast. I recommend you to book in advance (by calling them) especially if you plan to go there on a weekend, the rooms are full weeks in advance. Prefer to go there during weekdays, you will have more chances to get a room.
When the rice season is over, it does not worth to come, you would be very disappointed. Besides, the guesthouses are closed.
Alternatively, you can come by your own means (rental scooter or car) up to Mae Pan waterfall but leave your vehicle in the car park of the waterfall and ask the guesthouse to send a 4x4 car to pick you up for the last 3 kilometers. The wide rough road is often very muddy and not easy if you don't have the right vehicle and are use to it. The roundtrip with the pick-up will cost you 700 THB regardless of the number of passengers. You will pay when you leave Ban Pa Pong Piang.