The full packing list covers everything. This is the ruthless version: the handful of items that visitors most often get wrong, from someone who has watched a lot of people arrive under-prepared.
1. Leech socks. Actually buy them.
Every trip, someone treats leech socks as optional and spends three days flicking leeches off their ankles instead. They're cheap in Lahad Datu, they turn the trail leeches into a non-event, and they cost you nothing to pack. This is the single highest-return item on the list.
2. Quick-dry, not cotton.
Cotton in this humidity stays wet from the moment you sweat until you leave. Two or three sets of lightweight synthetic or merino long sleeves and trousers — neutral, non-rustling — will dry overnight under a fan and cover you against sun, insects and scratches. Pack light; laundry is available.
3. A proper head torch (and a spare).
Pre-dawn starts, night walks, the path back from dinner: you need both hands free and reliable light. Bring a spare torch and spare batteries. A red-light mode is kinder to wildlife and to the people beside you.
4. Dry bags, more than one.
The afternoon downpour is not a possibility, it's a schedule. One dry bag for the daypack, one for camera gear, one for documents. Silica sachets in each — the humidity gets everything eventually.
5. Cash from Lahad Datu.
There's no ATM in the forest and limited card use. Draw what you need for tips and incidentals in Lahad Datu on the way through, along with travel-sickness tablets for the gravel road. Get these two things right and the rest is detail. Everything else — insurance, the entry conditions, the humidity care for cameras — is on the entry rules and full packing pages.