How to Get to Khao Sok National Park from Bangkok

Visiting Khao Sok National Park is one of the most amazing experiences that you could ever have in Thailand. It is one of the biggest national parks in the country, with some of the most stunning landscapes and wildlife.
If you are traveling from Bangkok or the north of Thailand, I recommend flying into Surat Thani Airport. This is the closest airport to Khao Sok National Park and therefore the most convenient.
Flying from Bangkok to Surat Thani Airport

From Surat Thani, it is about a two-hour drive to the national park. To complete this journey, you can either hire a private driver for around 2,200 Thai Baht, or you can hop in a shared minivan for around 350 Thai Baht.
A private driver is obviously better if you hire one. They will be there waiting for you at the airport, ready to take you directly to the national park, and they will also be able to stop off wherever you want if you need them to.
Surat Thani to Khao Sok by Private Driver or Minivan

Understandably, though, you may want to save a significant amount of money by taking the shared minibus. With the shared minibus, you have to make your way from the airport to the bus stop.
The buses run from Surat Thani Bus Station to Khao Sok National Park about every hour from 6:00 a.m. to 4:00 p.m. There are also services that can help organize your trip to the bus station from the airport, and it should cost about 100 Thai Baht.
Traveling from Bangkok to Khao Lak by Bus

I do not recommend doing this, but there are actually buses that run from Bangkok to Khao Lak. They usually leave in the evening, travel all night and then arrive in Khao Lak in the morning.
They take about 16 hours, which is why I do not recommend them, and they cost around 1,000 Thai Baht per ticket. These buses leave from Khaosan Road or the southern bus terminal.
How to Get to Khao Sok from Phuket

If you are traveling from Phuket, the cheapest way is to get a bus that runs from Bus Terminal 2. This is about an hour’s drive away from the main tourist areas of Patong and Kata, so you have to make your way there first.
Buses run multiple times a day, take four hours and cost 370 Thai Baht. You can also arrange a shared van that will pick you up from your hotel, which is considerably more convenient because you do not have to make your way to the bus station. Tickets for this cost around 1,000 Thai Baht per person.
If you want a private taxi, I am seeing a range of prices from as low as 2,500 Thai Baht to as high as 3,800 Thai Baht. To be honest, I think that is a pretty decent price for a journey of more than three hours.
How to Get to Khao Sok from Krabi

From Krabi, all the same options apply. The public bus runs multiple times a day from Krabi Bus Station, takes four hours and costs around 400 Thai Baht.
The shared minivan that will pick you up from your hotel only costs around 500 Thai Baht, so I think this is considerably cheaper and probably the best option for most people. It looks like this only runs around 11:00 a.m., so I would try and book this in advance so it does not fill up, although there may be multiple buses that run around 11:00 a.m.
For a private taxi, it costs 2,800 Thai Baht.
Traveling from Koh Samui Koh Tao and Koh Phangan

If you are traveling from the Gulf of Thailand, from Koh Tao, Koh Phangan or Koh Samui, you must first get a ferry or a boat to the mainland and then catch a bus to Khao Sok.
Luckily, this can be done with a single ticket, so you do not have to worry about the transfer. Someone will be there waiting for you at the pier to help transfer you to your bus. Bus and boat tickets can be bought for around 800 Thai Baht.
If you want a private taxi, the prices I am seeing are 8,000 Thai Baht from the pier to Khao Sok, which to me seems way overpriced. I would stick to the bus and boat ticket.