How to reach the resort if coming via ferry?
You can take a pick up taxi that will cost you 100 to 400 THB to your resort on the island. 200 THB toward middle of island + fee of national park per person. Can not remember how much exactly but around 160 THB for entry. 'Tis.
Taxi is easiest. We usually rest a scooter near ferry and drive over. It's a bumpy hilly walk but you can do it if not carrying much baggage.
Been here about 20 times... When you exit the ferry you can try to sneak past the dock security to avoid the 20b fee, or pay that before leaving the ferry port. Then turn to your right and find the green trucks (songtaew taxi). Tell them Ao Tubtim or Tubtim Resort. Should be 40b/person. The truck will stop at the National Park Entrance and you'll pay 200b/person for foreigners or 40b for locals/ Thai work-permit holders.
You can avoid the national park fee if you walk through town and all the way to the the hotel- it should take about 45-60 minutes and most of that is on the beach.
Get an answer from Tub Tim Resort staff and past guests.