Ko Kut (also Koh Kood) is an island in Trat Province in the Gulf of Thailand and the easternmost island before Cambodia. The island is a popular spot for package tourists and families. The island has virtually no night life, so if you are after partying this is definitely not the place to go.
Boonsiri High Speed Ferry  or Koh Kood FantaseaCatamaran  . These two are the same, just different calling. (starting on 15 November 2013) 600 THB per person one way or 1200 baht per person incl. bus transfer from Bangkok. Pick up point in Bangkok is Khao Sarn Road and Shell Gas Station in Bang Na, at 7-8am. Sailing time between 70-90 Minutes. Departures at 2pm. daily from Laem Sok to Koh Mak(Ao Nid Pier) and Koh Kood(Bang Bao Beach), also during low season. free taxi from Trat to the pier in Laem Sok and Koh Kood.
The connection to/from Bangkok via the pier at Laem Sok is seamless and easier than arranging your own transport. The return trip will also stop at the Lat Krabang airport link station, which is just one stop away from BKK Suvarnabhumi Airport. Beware of elastic time if you are trying to connect to a flight, the 12pm boat from Koh Kut has been known to leave up to 1.5 hours late.
However. do note that during 15 May-15 October which is considered monsoon season, Boonsiri's departure time is changed to 11.45 from Trat to Koh Kood, and 9.45 from Koh Kood back to Trat.
Ko Kut Express  350 THB per person one way. 1h15m. The boat ticket includes a free taxi from Trat to the pier in Laem Sok and on Koh Kood from the pier to your resort. Taxi's in Trat depart from the Market near the big clock/thermometer or your accommodation. Leaves the market in Trat at 11:30 sharp! Departs from Laem Sok daily at 01:00pm. Departs from Koh Kood daily at 10am, also during low season. The free taxi from Trat will pick you up only when you made a reservation 48 hours prior to departure. The website offers a multilingual 24h chat to help you with that (although there might not be anyone awake if you decide to take the "24h" part literally). If you're lucky, you might be able to arrange a deal while you're on the way to Trat even if you didn't made a reservation. This heavily depends on the goodwill of the person you're chatting with though.
Koh Kood Princess  350 THB per person one way. 1h15m. The boat ticket includes a free taxi from Trat to the pier in Laem Sok and on Koh Kood from the pier to your resort. Taxi's in Trat depart from the Market near the big clock/thermometer or your accommodation. Leaves the market in Trat at 11:30 sharp! You can also buy ticket at Trat Bus Station. Departs from Laem Sok daily at noon. Departs from Koh Kood daily at 10.30am, also during low season.
Update: Koh Kut Express now uses the same boat model as KK Princess! Old: Note that despite the same ticket price, same departure time, and same duration time, the difference between these two ferry companies is the boat. Koh Kut Express's Boat has only indoor seats with only one exit, though you can sometimes sit on the roof of the ferry with the cargo. While Koh Kood Princess's Boat is bigger, with both indoor and outdoor seats, and many exits.
The other difference is the arrival pier in Koh Kood. Koh Kut Express arrives at 'Nam Luek Pier' which is on the west coast, where virtually all of the resorts are located. And Koh Kood Princess arrives at 'Ao Salad Pier' which is on the east coast, and will involve a 30+ minute ride from the pier to your resort.
Siriwhite Speedboat / CP Laem Sok Group  600 THB per person one way. 60-90 Minutes. Two speedboats depart daily from Laem Sok on the mainland near Trat. Stops are made on demand at most west coast piers on Ko Kut, finally terminating at Ko Kut's Bang Bao Bay. Boat departs from Laem Sok at 9am and depart from Ko Kut daily at 12pm. The speedboat tickets also include a free taxi from Trat to Laem Sok pier. The speedboats do not operate during low season due to the weather conditions.
Koh Kood Speed Boat / Ao Thai Marine Express  This service is only available for private charters.
Note that the boat fee (350 baht slow boat, 600 baht speedboat) includes transport to/from Trat, but only when using taxis that are assigned by the boat companies. If you take the speedboat, you will usually be dropped at or very close to your destination.
To/From Koh Chang
Kai Bae Hut Express  (speedboat) 900 THB per person one way. Daily from Kai Bae pier on Koh Chang at 9am.
Bang Bao Boat  (speedboat) 900 THB per person one way. Daily from Bang Bao pier on Koh Chang (9am & 12pm)
The trip can take 1-2 hours depending on conditions and the number of stops at the islands between Koh Chang and Koh Kut, (Ko Mak, Koh Wai, etc.) and the number of stops around Koh Kood. The boat ticket includes a pick up or drop off at most hotels on Koh Chang.
Public taxis are available. Rates & times are not quite standardized yet, but that should not be long. Siam Beach Resort (located in Bang Bao Bay) also runs a taxi service. Another fun way to travel around is by motorbike. Expect to pay around 300-350 baht per day, resorts often charge 400-450 THB but also rates about 200-250 are possible outside of main season. Road conditions vary between dirt roads and paved roads but since 2009 there is a small concrete road covering the Western coastline from North to South. Maps are available though a bit confusing. Bicycles can also be hired (around 150 baht per day), but the heat and the hilly nature of the roads makes them of limited usefulness for all but die-hard cyclists. For those that are not in a hurry: small fishing boats can be hired to tour around the island.
Swimming in the crystal clear waters, sunbathing (there can be sand-flies depending on beaches and season), scuba-diving, snorkeling, kayaking, jungle trekking, trekking to the waterfall or just relax and read a book.
There are virtually no towns on Ko Kut so sightseeing is pretty limited. The fishing village of Ao Salat (northeast island) is home to around 300 people, making it the largest settlement on the island. The village is built on stilts in the water, and is quite interesting and well worth the the rather long road trip to get there. Expect to pay around 500 baht for the trip as cars are quite scarce. Or rent a scooter to get around.
Scuba diving is a great way to discover the underwater world around Ko Kut. Diving off Ko Kut is easy, fun, and you can see turtles, stingrays, barracudas, lots of small fish and sometimes sea horses.
Nearly any time of the year except from July till end of September is good diving weather in Ko Kut and visibility can exceed 30 m. Average visibility is around 15-20 m. From July till September visibility is reduced to 5 m and the seas are choppy.
It is possible and perfectly comfortable to swim and dive without a wet-suit year round. However, as with most diving, a wet-suit is recommended to help reduce risk of cuts or injury. Avoid contact with coral reefs.
Various dive locations around Ko Kut are:
There is a souvenir shop in Ao Salat. Other than that, you'll be hard pressed to find anything in particular to buy outside your resort. There are no chains like 7Eleven or FamilyMart around, but daily necessities can be bought in numerous small shops around the island. Note, however, that there is only a single ATM on the island which might very well be out of order. It is located near Koh Kood Wittayakhom School, the District Office and the Police Station.
Many of the resorts, but not all, have good restaurants. Outsiders are always welcomed . Now also a few restaurants are popping up including the rustic locally-run Chiang Mai Restaurant (by far the best food in koh kut. Big portions, amazing tastes and really cheap. Make sure you visit and try the sweet red curry)  and a Thai/Italian-run Italian pizza and pasta house . But for the ultimate in ambience View Point Cafe is tops. Located on top of the waters of Klong Chao with great views across to the ocean. Prices on Koh Kood are slightly above mainland. The cheapest feed is roughly 60 baht for a bowl of noodles. Expect to pay 80-200 baht for a main course at non high-end places (usually 100-150 baht).
If you want to cook for yourself then a small selection of fruit/vegetables is available at a stand/shop operating some distance across the bridge from Ban Klong Chao, before the Sunset Bar. Basic staples and ice cream are available at a number of shops around the Khlong Chao.
For high season (November - February) it is recommended to book ahead, especially in weekends. Although there are many different places to stay, most of them can easily be fully booked during Thai holidays that Western tourists are usually unaware of. Also, apart from the Klong Chao area, Koh Kood is not an island where you can easily stroll from resort to resort.
About 40% of the resorts remain open during the rainy season (May-September). Expect services to be limited during that period. Some restaurants, bars & shops close, diving is not always possible etc...
Accommodation is widely spread out over the island with Klong Chao in the middle where most activity is. Low budget/backpacker accommodation can be found there. Most beach resorts are connected to the main concrete road by dirt tracks.
Compared to neighbouring Ko Chang, infrastructure is much less developed. Electricity regularly cuts out, and many resorts do not have backup generators. Some resorts offer Internet access (such as Siam Beach Resort, Hindard, and Koh Kood Resort) while others do not. Internet appears to be offered via 3.5G UMTS (i.e., mobile, speed may depend on provider) and is prone to dropping out. Mobile phones with "Happy DTAC" SIMs work on 3G (decent speed) other networks unconfirmed.
Local tourist information is hard to come by, but Internet searches will reveal maps of the island.
NO BANKS! Take cash. Only one ATM on the island. Only higher-end resorts take credit cards. If you run out of money, second-hand sources report that credit card cash advances are possible at the larger resorts for a 5% fee.