This is my 2nd time to write this !!!
I advice you to visit both Sabah & Sarawak plus Brunai. I was there during 2005 and I have done that. For National Parks, Culture, and sleeping in the houses of the orginal people of Borneo this will gonna be Sarawak. for Nice beaches, Snoerkelling, and jungle tours this will gonna be Sabah. Brunai is just on your way from south to north so it will be good to pass by another country.
1. Bako National Park, to see the probiscs monkeys. (day trip from Kuching).
2. Refflesia flower (I think the biggest flower in the world if iam not mistaken. do it from Kuching).
3. Orang Asli Long houses in Belagan. You can go by Ferry (which I did) or you can fly. Let me know if you need more details about this. Not necessary Belagan but this was the cheapest way for me and it was such an unforgatble memories. You should.
4. Niah National park. Just Caving. Maybe you can skip in you are not intrested in Cavings, but if iam not mistaken i think it's the biggest in either Malaysia or SE Asia (not sure).
4. Mulu National Park (Fly from Miri). You should give it a visit and climb the mountain from camp5 and see the Pinnicals.
5. Kelabit Highlands (Fly from Miri). I was not able to go due to the weather. Try to gather more information about it.
6. Enter Brunai via a bus from Miri and stay a night in BSB.
1. YOU SHOULD climb the Kota Kinabalu mountain. Dont go to the national park if you have not booked your accomendation in the 11,000 feet camp. You can do that in KK city as they have an office there. Ask around.
2. There is nice islands near to KK city and its beatiful (day trip).
3. I DONT advice you to see the Orang utan in Sepilok. It was more like a zoo to me and not what i have expected.
4. YOU SHOULD go to a Jungle tour and sleep there 2N/3D. Try to get uncle Don (I cant remmber the name but 99% it's right, hehe).
5. YOU SHOULD go to Sipadan Island for snorkelling. Note that you are not allowed to stay in Sipadan, so You will stay in Mabul Island. Uncle Chang is the only guest house for backpackers and I advice you to book in their office from Samporna for the snorkelling trips. They are very nice and Very Friendley.
That was the main places i have visited wihtout the transait here and there.(expect Kelabit and the Reffleisa as the flower is availabe in certian times only, u will be lucky if u will ge the chance). Let me know if you need more details. Just Ask here and I will reply you. I hope this will help you and dont forget the Lonely Planet book.
Happy Travelling 😊