Ko Jum (เกาะจำ) is a small island between Ko Lanta and Krabi Town. While the south end of the island is known as Ko Jum (or Jam or Cham), the northern part is also called Ko Phu (or Pu), and local villagers take fierce pride in the two different names.
Ko Jum has three main villages and is home to about 1500 permanent local residents. On the west side of the island are about 20 resorts which provide very simple bungalow accommodation.
Most travelers arrive via the ferries that connect Ko Lanta and Krabi, which charge about 350 baht (the same price as for the entire crossing, even though Ko Jum is at the half way point). The fare can be paid on board, but pre-booking is recommended as the ferry is often full. Tickets can be bought from travel agencies in Krabi or at the main ferry offices at the old pier on Thanon Khong Ka, and with resorts on Ko Jum. Ko Jum has no jetty or dock - the ferry stops offshore and is met by longtail boats. If you've pre-booked, then a boat from your resort should be there to pick you up; otherwise simply choose one and ask for a lift to shore.
The Krabi-Lanta ferries run only during the high-season which typically starts between 12th & 14th November and ends in April (it varries every year and you should check with your hotel beforehand). During the low season you would have to charter a longtail boat. From Krabi Town or Ko Lanta this will cost you around 2,500 bahts one way. You can however make the trip via Laem Kruat which will be considerably cheaper.
From Krabi Town, you can take a songthaew (small open minibus) to Laem Kruat. The songthaew should be blue and white in colour and you can hop on it outside of the 7/11 shop or the Siam Bank branch near Chao Fah pier. Ask the driver to confirm the destination. You may have to change at Nua Khlong. The trip to Nua Klong should cost around 20-50 bahts and from Nua Khlong to Laem Kruat around 40-50 bahts.
There should be ferries from Laem Kruat to Ko Jum between 11:30 a.m. and 6 p.m. costing 70 baht (for foreigners). Prices correct as of May 2012. It is a 40 minute boat ride.
Transport at Nua Klong (leaving every 30 minutes) to ferry is outside the general store 30 metres down the road with traffic lights. This will be just behind you if you get dropped off at a motorbike taxi stand. Ignore them and walk.
Ferries to Ko Jum (July 2013) at 9, 10, 11.30, 13.00, 14.30, 16.00, 17.30 and 18.15 according to the sign and cost 50 baht.
Ko Jum is a relatively small island and most of the population gets around on small 100-125cc motorbikes, which can be rented easily. There is also a local taxi service, comprising a motorbike and sidecar! The roads between the villages are narrow, unsealed, and frequently pot-holed and wet, and can be very challenging for inexperienced riders. There is now a concrete road surface in the three villages and on the stretch between Ban Ting Rai and Ban Koh Jum. A taxi ride from the Ko Jum ferry port to most places on Ko Jum South is 50 baht (as of May 2012). You can also be driven around if you want to see the island's main places for 400 baht (as of May 2012).
The villages are sights in themselves, with slight differences in their ways of life. Travelling around the island on a motorcycle is a fun and (mostly) safe way of sightseeing.
Most resorts will also be able to arrange daytrips with treks up to the top of Mount Pu on the northern part of the island, which has a majestic view of the islands and the Andaman Sea.
Relax in a hammock by the beach. Swim. Walk along the beach. Small hikes. Many people seem to stay here longer term just to relax and recharge. There is not a whole lot of activities to do.
Most guesthouses and resorts on the island have a kitchen, and would be happy to take your order even if you aren't staying there as a guest. Just walk down the beach until you get hungry. The meals are good, and the prices decent.
The island just recently got electricity (2008) and it's starting to get developed in the southern part. The constant loud noise from bars and partygoers, like it is at Phi Phi, has not been an issue here, but this will probably change with time. Beer and stronger drinks are available from your guesthouse, or from shops in the Ko Pu, Ting Rai and Ko Jum villages.
Respect the locals by making an effort to keep bottles of alcohol out of view, and keep in mind that many travellers come here to get a quiet break from these parties that you'll find anywhere else in Thailand.
It seems unlikely that there are any problems on Ko Jum but take usual precautions.
An exception may be dogs, particularly in low season and they may become more desperate for food and attention (which tends to come from tourists not the local muslims) and/or territorial. This reviewer was adopted and bitten by a dog, chased out and later prevented from entering a resort from the owners dogs and accosted by another pack in the space of three days in July 2013.
Some people go to Ko Phi Phi or Ko Lanta via ferry. Otherwise if you want to go back to Krabi Town, just go back the opposite way you came in. The ferries back towards Krabi Town, via Laem Kruat, go from 7:15 to 8 am.