I spent some days at this place. I booked a bungalow with garden views but still managed to sea a little bit of the sea since it was on the second line. It was pretty basic but clean. I liked how cozy it was, also the bed and pillows were comfy. I disliked how hot it was inside, there's a fan on the ceiling but it was very slow and I could barely feel the air, so after requesting it I got a standing fan which made such a difference. There is NO fan downstairs where the bathroom is located.
They should get rid of the towels and bedsheets, they are so old and even though they had been washed they just didn't smell good, because it is time to change them. Bedsheets also were hard and had some permanent stains on them.
Location in Sunrise Beach was good. WiFi was nonexistent, in case you need it, don't count on it. There is a very cool restaurant with several sitting areas. During my stay they did not serve food (low season) but we could bring it from outside and eat it there. No chance to refill my bottle of water at the resort and if you buy it there it's very expensive, so it's better if you buy it at the 7/11.
The member of the staff who I dealt with during my stay, Nut, was very helpful and attentive and he always had a smile. I have to clarify that I went during the low season, right beginning of July when the island reopened after the Covid. Therefore, I had a good deal and I'm satisfied with what I paid. But I wouldn't book this place in high season and I wouldn't recommend it either since prices are way too high for what you get. (I live in Thailand and I checked them a few times plus I was in Koh Lipe a few months ago).
Lastly, there's also a small diving shop but the guy who works there (not sure if he was the manager) let's say he was not very welcoming. Despite being a diver I decided not to dive with Castaway Resort. I would recommend Ko Lipe Diving School instead.