Hiya, You would need the patience of a saint to bus from Balikpapan up that coast. There are buses from Balikpapan to Berau, and onwards and upwards, but it's at least 23 hours just for that leg and can be double that if the road's bad -- most locals fly.
Regular ferries run from Tarakan to Tawau. I would recommend picking up a flight to Tarakan from Balikpapan -- a number of local airlines run this route and either a travel agent or the airport ticket desks can help you. Then it's a couple of hours on the ferry, plus a fairly lengthy bus ride. Or you can fly internally from Tawau-Semporna.
You won't be able to book tickets online, though, because it's all small local carriers on both sides of the border. There are no flights that cross that border without routing through random places.
#2 TheodoraZ has been a member since 25/7/2011. Posts: 6