Sarah is correct. I stand corrected as I was wrong. I was thinking about a place near Rayong, whcih was why I was wondering why you wanted to travel that far with so few days.
Sarah, there used to be a hovercraft years ago that transported people between Rayong, Pattaya and Bangkok, and I thought the Hua Hin area as well. Probably not used anymore, even when it was running I didn't think too many people used it. I think it was mnore of a hydra foil than a hovercraft.
I am assuming that you are considering splitting up the four days between Cha Am and Hua Hin?
Probably staying in each place is the best as I don't think it really makes any difference as far as time is concerned. Time is really the issue here. Is there a reason why you want to or have to do both places? To get from one place to the next is going to take some time. Bus transport is probably the most reasonable. Consider 3-4 hours from Hua Hin to Bangkok, transfer and then another 2-3 hours to Cha Am. Basically a whole travel day. You may do it a little faster if you took private taxis or shuttle. You may consider water transport, probably faster "if" that is an option. Years ago there used to be a hovercraft out of Pattaya, into BKK and I think Hua Hin but that was a long time ago. You'd have to go on-line and find out if that is still an option but I have not heard of it lately. Have no idea on time.
If you don't have to do both places, do one and just relax and have fun at the one place. You may find yourself scrambling to get from A to B. If you had more days, it would make a difference. That would be my advice. Otherwise, bus or private taxi are your options.
Lomprayah operate direct services from Hua Hin to Koh Tao and Koh Phangan. Their express bus to Chumphon and the board the Lomprayah fast boat catamaran to Koh Tao, this continues to Koh Phangan and also to Koh Samui
Train to Hua Hin from Hualamphong station (Bangkok)- about $6 - take the local, it's far more interesting. Try to get to Hualamphong before noon - the local's a 4-hour trip, stopping in numerous small towns, with vendors getting on and off, with baskets of snacks, cold water, etc. The daring can smoke at the open doorway between cars - also an excellent picture spot (use a fast shutter speed).
Returning to Bangkok from Hua Hin, the Sunday north-bounds have reserved seats. Try to buy your reserved seat return tickets as soon as you arrive if you're there for the weekend. They DO sell fast. Since we couldn't get a seat on the train going back, we taxied to Bangkok.
Taxi home to BKK, about $45 for 3 people. There's a world of stuff to see and stop at on the highway going north. That could be a road-trip in itself.)
Many people have told me before planning a trip to Hua Hin, they've never realised the long distance it is from Bangkok. It is about 3-4 hours by road from the new Airport depending on traffic conditions along Highway 4 which will bring you all the way to Southern Thailand. The roads are toll free outside of Bangkok.
Another option is to charter your Hua Hin hotel's taxi/car that will pick you up from Bangkok and the going rate is currently about 3000-3500 baht for a car one-way all inclusive.
You can get an express bus from the Bangkok Southern bus terminal. I've never taken that so I don't know how much that will cost.
The most expensive but quickest option is to fly from Bangkok via SGA airlines.
The BKK-Hua Hin air shuttle service offers travellers the option of flying between Bangkok and Hua Hin in 40 mins...The flight route passes over Bangkok, Samut Prakan, the Gulf of Thailand, the Chao Phraya River and the Petchburi province...
The airline operates 4 daily flights each way using a 12-seater Cessna aircraft... Ticket cost 3100 baht one way or 5200 baht return...
Probably the best decision I made during my visit to Hua Hin was renting a scooter. The greatest benefit of getting around by scooter is the flexibility; after all, you're not restricted any bus schedules or routes. In terms of safety, Thai drivers are used to many scooters on the roads, and I found them to be very courteous and cautious when passing.
Disclaimer: Be forewarned that there is a certain element of risk involved in renting a scooter. I purchased an "insurance agreement" for a few extra dollars, but to be honest, I'm not really sure how much legal legitimacy these actually have. So if you get in a wreck, regardless of who's at fault, I really have no idea what would follow....
Quick tip: Take a few pics of your scooter before leaving, to prevent being accused of damage you're not responsible for.
Cost: about $8 for manual transmission; $13 for automatic per 24 hour period. The manual isn't particularly difficult to learn, but automatic is probably worth the extra $5 for beginners.
Bottom-line: An economical, efficient means for getting around Hua Hin. Highly recommended for those who can't afford rental cars.... Can be chancy in that the consequences of getting in an accident are uncertain, but just don't drive like an idiot and you should be fine.
This a bus you can take further south, down as far as Pranburi past Khao Tao and Suan Son Beach. Buses leave from the intersection of Phetkasem and Chomsin Road (just north of the Night Market) about every 20 minutes from 07:30-17:30 daily.
Cost: about 10-15 baht
Green and Red songthaews cruise up and down Hua Hin's main drag (Phetchkasem Road) at least every 15 minutes. Most go as far south as Khao Takieb, and pretty far north as well. A good place to catch one is near the Night Market on Decha Nuchit Road.
Cost: about 10 baht per trip
I found that you can easily walk around Hua Hin to find whatyou are looking for. Around the area I was staying, I could access the beach, shopping, and great restaurants all within short walking distance from my room. The main street in Hua Hia is quite busy to cross during the day, but lucky they have an overpass to make it easier on you (see picture). I think here it was much better to walk it rather then driving around, it is a great way to explore the city.
Bicycle and motorbike are readily available for rent at very decent price. If you have a hotel a bit out of town, it may be a good idea to rent it as soon as you get off the bus or the train.
Price vary between 50 to 100 Bath for a bike and 200 to 300 for a motorbike
To go to Takiab and come back, forget about the taxi asking you for 100 Bath one way. As everywhere in Thailand, along the main roads some pick-up fit for passenger are available at very cheap price. 10 bath in Pattaya and 8 here in Hua Hin.
As the trains to Bkk were not really matching the schedule, I decided to take the bus to go back to Bkk. It takes 3.5 Hours including the 20 min break for the crew to refill their stomach. The journey was ok and a lot of seats were empty so I could sleep comfortably !
Paid around 135 Baths
There are many places where you can rent motorbike or car if you like to travel around by yourself. Hua Hin is not too complicate to travel around in my thought, just only you need a good map in your hand, and go...
Inside the town I think motorbike is more suitable, all street/ roads are quite small. To go further outside the town, you can drive a car.. such as to Khao Takiab, to Cha Am beach or other beaches nearby.. etc
The best way to look around Hua Hin town, I strongly recommend, doing it by walk. Seriously..!! it's the best way !! Hua Hin town all the streets are connected and every part always has something different and interesting, you cant see if you ride a motor bike or drive a car. Mostly interest places are in walking distance, just only you want to visit Khao Takiab, that 's far away from town then you better look for other choices..