One train per day departs from Bangkok's Hualamphong station at 15:35 and stops in Pranburi around six hours later. Fares run from 48 baht for third class up to 225 for first class. This train also stops in Hua Hin.
Many of the southbound regular buses from Bangkok's Sai Tai Mai (Southern) terminal stop in Pranburi and leave regularly throughout the day. You won't necessarily see a sign for Pranburi on the ticket booths, so inquire at any booth advertising buses to Prachuap Khiri Khan, Chumphon or Surat Thani (among others). Buses from southern points can also drop passengers in Pranburi.
In Hua Hin, orange local buses depart for Pranburi every 30 minutes from the corner of Sa Song and Chomsin roads, cost 20 baht, and take around an hour. You can also flag these down as they pass by anywhere along Phetkasem Road.
Minibuses (vans) depart from Sai Tai Mai (Southern) bus terminal in Bangkok. These normally drop off at Tesco Lotus in Pranburi but we were told it's possible to pay the drivers extra to take you straight to Phu Noi beach. The cost to Pranburi is 220 baht. Minibuses running between Hua Hin and Prachuap Khiri Khan can also drop passengers in Pranburi.
As there's no direct public transport to the national park or Phu Noi beach, you must first pass through Pranburi, some 20 km north of the park. From the bus station, songthaews costing 50 baht per person run every 30 minutes from 8:00 to 16:00 to Bang Pu, which is walking distance to Laem Sala and the national park accommodation at Phraya Nakhon beach.
Otherwise you can hire a private songthaew or car to Phu Noi beach for between 400 and 500 baht, or motorbike taxi for between 200 and 300. Be sure to tell the driver your specific destination (i.e. Laem Sala or Haad Phu Noi). Many of the resorts on Phu Noi can pick up guests in Pranburi for around the same price.
If you have your own wheels and are coming from Hua Hin or elsewhere in the north, follow Phetkasem Road (Route 4) or AH2 to Pranburi (the two roads merge) and hang a left on to Route 1020 at Tesco Lotus, a few km north of downtown Pranburi. You can follow this all the way into the park or take a left (east) at Wat Phu Noi to access Phu Noi beach. Alternately, a left at the main intersection in downtown Pranburi puts you on Route 3168, which links with 1020 after a few km.
If coming from the south on Route 4 / AH 2, take a right on to Route 1026, following signs for park headquarters, which will bring you across to the southern side of the park.
You'll need some wheels to get around the park. Motorbikes can be rented at most of the resorts on Phu Noi beach for between 250 and 350 baht per day, and there's also a stand at the centre of the beach road with a few motorbikes for rent. Dolphin Bay Resort has the best selection. Bottles of petrol can be purchased at a handful of small convenience stores scattered around the area.
Regular pushbikes can be rented at Sam Roi Yod Holiday Resort and Dolphin Bay Resort (among others) for 100 baht per day, and Dolphin Bay offers quality mountain bikes for 200 baht. You could reach Laem Sala on a bicycle, but it would be a long and hot ride; most use the pushbikes only for getting around the Phu Noi area.
Cars with drivers can be arranged at national park headquarters and the resorts on Phu Noi beach, and cost 800 baht for a full day. Expect to pay a bit more if you want to hit Thung Sam Roi Yot.
Longtail boats can be hired through resorts on Phu Noi or directly at Laem Sala and Khao Daeng. Expect to pay between 1,000 and 2,000 baht for a tour of some of the islands, mangrove forests and/or coastline. Kayaks can be rented at several places on Phu Noi beach, though we did not see any at the national park beaches.