The first Full Moon Party is said to have been improvised at a Paradise Bungalows on the beach in 1983 as a token of thanks to about 20–30 travelers, though the accuracy of this is disputed, as is the date of the original event. The parties gained fame through word of mouth, and the event now draws a crowd of about 5,000–30,000 every full moon evening.

The night begins when a full moon appears over Haad Rin beach. Local businesses – restaurants and bars- and the organisers will line small tables along the beach and thousands of traditional Thai lanterns are lit to commemorate the start of the event. Start your night at Haad Rin, where you get the authentic taste of Full Moon mayhem. The bars on Sunrise Beach of Hat Rin stay open and play music such as psychedelic trance, R&B, drum and bass, house, dance, and reggae.  Its attractions include fire skipping ropes, alcohol “buckets”, and drugs. 

The Full Moon Party takes place every month throughout the year. Everyone has to pay a 100 baht entry fee to get the Full Moon Party wristband. Tour companies also offer Full Moon Party packages, which include your entry, transportation etc. Hotels and hostels also offer reliable Full Moon Party packages. They may also have their own organised transport service for guests.

According to Wikipedia and timeout.com