I made contact with one guiding service and they've quoted me 6500B for a full day birding trip to three different places on the island, including Ton Sai waterfalls and Bang Tak non-hunting area (sic). The fees cover tranportation, meals, entrance fees and guiding services. I'm joining someone who already signed up with them. As I understand it, it's just the two of us, so it's quite personalised. Still, 6500B (S$273) feels like a lot of money so I'd like to see what options are before biting the bullet.