644km (400 miles) S of Bangkok to Surat Thani; 75km (47 miles) NE from Surat Thani to Ko Pha Ngan

While Ko Pha Ngan lost its innocence years ago to the Full Moon partygoers (see below), the island still remains a more pastoral alternative to busy Ko Samui. When the moon is waning and waxing, the island, just like a chameleon, changes back to a laid-back, tropical paradise where almost 90 percent of the island is covered in tropical forest. Just off the shores are top-rated diving and snorkeling sites.

Easily visible from Ko Samui but about two-thirds its size, with similar terrain and flora, Ko Pha Ngan boasts beautiful beaches and some secluded upmarket resorts on the farther reaches of the island -- the rugged north and west coast areas are accessible only by bumpy road, or chartered boat. The southeastern peninsula of Had Rin (also written Haad Rin) is home to the now-infamous monthly Full Moon Party, a night-long beach rave that attracts thousands of revelers who pack the island to groove to every kind of dance music -- and consume (and usually later regurgitate) buckets of alcohol. For those who can't make it for Full Moon, there are also (smaller) Half Moon and Black Moon parties-check out http://fullmoonparty-thailand.com for dates. These parties are no longer the hippy, trippy, lovefests of the '70s, but blatantly commercial gigs geared to squeeze as much cash out of revved-up partygoers as possible. As evidence of this, there is now a 100B entrance fee to the Full Moon Party. At Full Moon, even the basic bungalows are going for double the normal rates. As a result, Leela Beach, on the northern spur, now pulls more punters than the noisier beach at Had Rin Nok (known as Sunrise Beach).

Boats from Ko Samui leave at regular intervals all day and night on Full Moon nights from either Big Buddha Beach or Bophut (running from 5pm; returning btw. 3 and 8am). Many revelers just make a night of it, crash on the beach, and come back to Samui in the morning. At other times, the small area of Had Rin is busy with young travelers. You'll find New Age crystal, trinket and T-shirt shops, vegetarian restaurants, bars playing DVDs, masseurs, cheap beer, and even cheaper bungalows just a Frisbee's throw away from perfect white-sand beaches. Be careful of the riptides here in monsoon months, and pay attention to the attendant lifeguards now present on the beach.

Don't be too put off by Ko Pha Ngan's party reputation. Had Rin can be avoided altogether and, even during the Full Moon, you can find peace and quiet in any of a number of tranquil hideaways on the island, such as Thong Nai Pan, to the north, and Had Salad or Had Yao, to the west. Ko Ma is a small island connected to Ko Pha Ngan by a sandbar on Had Mae Had beach. It's a paradise surrounded by an amazingly colorful, living reef -- making it an ideal location for snorkeling or learning to dive.

Two word of warning: Party time is also a petty thief's paradise. Do yourself a favor and lock all your valuables in the hotel safe before you party -- as experienced thieves take the opportunity to swoop on insecure accommodations while you're having fun.

More importantly when it comes to doing drugs in Thailand, remember that "mai" means "no." Thai authorities issue harsh penalties to anyone dealing, in possession of, or using drugs. Numerous undercover drug busts are staged, not just at Full Moon parties, but at bungalow hotels, and at pre- and post-party roadblocks. Many of these stings are setups that you'll never be able to disprove. Dealers and police often work in cahoots, and the lackadaisical Thai legal system offers you no protection or parole. Even scarier, recent reports have highlighted not just the selling of dodgy pharmaceuticals but the lethal herbal hallucinogen ton lamphong, a poisonous weed. Taking this is nothing short of suicide. Every month, local hospitals repeatedly find themselves treating tourists suffering severe psychological damage after taking recreational drugs or hallucinogens -- they are the lucky ones; some revelers simply go home in a body bag.