Here are the top places to visit and things to do in Thailand
Phuket
Phuket, which is approximately the size of Singapore, is Thailand’s largest island. The island is connected to mainland Thailand by two bridges. It is situated off the west coast of Thailand in the Andaman Sea.
In the 17th century, the Dutch, the English, and from the 1680s the French, competed with each other for trade with the island of Phuket it was named Junkseilon at that time, which was valued as a very rich source of tin.
In July 2005, Phuket was voted one of the World’s Top 5 retirement destinations by the acclaimed Fortune Magazine.
It is home to Hat Patong, Hat Karon, Wat Chalong, Thalang National Museum, Laem Phromthep, Khao Phra Thaeo Wildlife Conservation Development and Extension Centre. All of which are famous travel sites.
Most tourist travel to Phuket to experience its beautiful beaches and see the Phuket FantaSea: This is referred to as the Disney Land of South East Asia. It's the ultimate in night entertainment on Phuket.
Hin Daeng
Hin Daeng has good visibility, unless the waters become extremely plankton-rich. It is this plankton that attracts the larger marine-life and keeps everything well nourished.
Hin Daeng has the deepest drop off in Thailand, droping down to 70+m on the southern side. A large rocky outcrop forms a series of walls and ledges below the surface that are covered in red soft corals.
It is named after the beautiful red corals that cover the pinnacles. Due to the isolation of Hin Daeng and Hin Muang, they form the only reef feeding ground for a lot of surrounding ocean and therefore attract the bigger pelagics. Visitors could swim with huge schools of barracuda, rainbow runners, travellie, red-tooth triggerfish and batfish.
There is only one beach in Hin Daeng, the Hua Hin Beach ชายหาดหัวหิน Hat Hua Hin, it boast fine white sand, resort hotels and many water sports opportunities lend the resort its distinctive ambiance.
Phi Phi Don 
Phi Phi Don is the largest of the Phi Phi Islands, in Thailand. It is the only island in the group with permanent inhabitants.
Ko Phi Phi Don is now squarely on the tourist map, and tourists from all over the world flock to the island. Accessible from Phuket and mainland Krabi province, all tourists must arrive by boat.
It is known to travellers for the Viewpoint - walk up to the Viewpoint, 186 metres above sea level (a very steep walk of between 10-25 minutes, depending on fitness), to get a breathtaking view of the entire island - particularly at dawn or sunset (bring a torch). You will be surprised at how narrow the sand strip is between the two main parts of the island.
Damneon Saduak Canal
Damneon Saduak Canal is a canal in western central Thailand. It links the Tha Chin and Mae Klong rivers, and has a length of approximately 35 km. The canal was built by order of King Mongkut. It was finished in 1868.
The most famous site along the canal is the floating market in Damnoen Saduak. At the mouth of the canal to the Mae Klong is the catholic Nativity of Our Lady Cathedral, the principal church of the Diocese of Ratchaburi.
Koh Tao
Koh Tao is an island in Thailand located near the western shore of the Gulf of Thailand. The economy of the island is almost exclusively centered on tourism, especially scuba diving. Initially the island was not inhabited, there was only the occasional fisherman from the neighboring islands, looking for shelter in a storm or just taking a break before continuing his tiresome journey. The island is well known for scuba diving and snorkelling. Also offers some hiking, rock climbing and bouldering. The most popular place for tourists is Sairee on the West coast, which has a white sandy beach of 1.7 km interrupted only by a few huge boulders and a scattering of medium budget resorts and restaurants.
Koh Tao is home to the Master Divers Day Courses, a small professional centre on Koh Tao offering dive trips and a full range of PADI courses. It has a long standing reputation for offering a quality dive experience and maintains a friendly and relaxed environment. Master Divers guarantees small groups and offers private guiding and tuition too. Their team of multilingual staff are some of the most experienced on the island making the centre a sought after destination for divers.
West Railiy
West Railiy is a small peninsula located between the city of Krabi and Ao Nang in Thailand. It is accessible only by boat due to the high limestone cliffs cutting off mainland access. These cliffs attract rock climbers from all over the world, but the area is also popular due to its beautiful beaches and quiet relaxing atmosphere.
West Railay Beach is connected to the East side by paths through the large resorts or by trails through thin jungle cover it is the primary destination for beach-goers in Railay. The focal point of West Railay Beach is centered on a short promenade lined with restaurants and shops.
Koh Phangan
Koh Phangan is an island in the Gulf of Thailand in South East Thailand. It is famous for its full moon party at Haad Rin Beach and as a backpacker’s destination. The Bronze Drum of Dongson Culture (500BC - 100BC) that was found on Ko Samui in 1977 is evidence that there were settlements of people on Ko Samui, Ko Pha Ngan, and their islets from more than two thousand years ago.
It is known to travellers for the Full Moon Party, which often involves electronic music, occurs on Ko Pha Ngan every full moon of the month. Recently, though, steps have been taken to make Ko Pha Ngan into a more family-friendly tourist destination.
Most travellers to Koh Phangan also liked Than Sadet-Ko Pha-Ngan National Park, the Park which is free of charge is named after the river Than Sadet.
Ko Samui
Samui is an island off the east coast of the Kra Isthmus in Thailand, close to the mainland Surat Thani town. The island was probably first inhabited about 15 centuries ago, settled by fishermen from the Malay Peninsula and Southern China. It appears on Chinese maps dating back to 1687, under the name Pulo Cornam. It is surrounded by about sixty other islands, which compose the Ang Thong Marine National Park (Mu Ko Ang Thong National Park) and include other tourist destinations (Ko Phangan, Ko Tao and Ko Nang Yuan).
Chaweng Beach is the major beach on Ko Samui and one that has developed tremendously since the early 1990s. Just 20 years ago the beach was home to just a sprinkle of wooden bungalows but now the place is swamped with 4-5 star hotels, Italian pizza joints, Irish pubs and even go-go bars. Samui’s nightlife is becoming legendary but unfortunately not always attracting the best standard of tourist.
Ayutthaya
Ayutthaya was a Siamese kingdom that existed from 1350 to 1767. In the sixteenth century, it was described by foreign traders as one of the biggest and wealthiest cities in the East. The court of King Narai which existed from 1656 to 1688 had strong links with that of King Louis XIV of France, whose ambassadors compared the city in size and wealth to Paris. The ruins of the historic city of Ayutthaya and "associated historic towns" in the Ayutthaya historical park have been listed by the UNESCO as World Heritage Site. The city of Ayutthaya was refounded near the old city, and is now capital of the Ayutthaya province.
Chiang Mai
Chiang Mai is the largest and most culturally significant city in northern Thailand. In recent years, Chiang Mai has become an increasingly modern city and has been attracting over 5 million visitors each year, of which between 1.4 million and 2 million are foreign tourists. It has also recently positioned itself to become a Creative City and is considering applying for Creative City Status with UNESCO.
Most travellers go to Chiang Mai to see the Patara Elephant Farm, the farm invites tourists to a hands-on experience on participating, sharing responsibilities and taking care of an elephant. "Elephant Owner for a Day" is a special program created for everyone to learn and interact with elephants as what an owner would do daily, during which time you are trained to approach your elephant correctly, know the elephant's temperament, feed and check its health, learn about and take care of your own elephant, bathe and brush it in the river, learn how to ride on its neck, and communicate through different spoken commands. You will get a chance to bare-back riding to visit forests, waterfalls or local temples. The program is specialized and meaningful activity to create trust and relationship between you and your elephant.
Most travellers to Chiang Mai also liked the Siam Rice Thai Cookery School, the school offers a unique and enjoyable Thai experience. Cooking great Thai dishes for your family and friends is a gourmet souvenir that will leave a lasting impression.
Bangkok
Bangkok is the capital and largest urban area city in Thailand. Bangkok is by far the most densely populated city in Thailand with about 9 million people. Bangkok was originally a small trading post on the west bank of the lower Chao Phraya River during the Ayutthaya Kingdom. Today, Bangkok is one of the most important commercial centers in South East Asia and a gateway and principal destination for many visitors. It has more than 400 richly decorated temples, some of the biggest shopping centers in Asia, and six universities. Its numerous canals, some of which are home to floating markets, give Bangkok the name "Venice of the East."
Favourite destination by travellers is the Temple of the Reclining Buddha (Wat Pho), it is one of the oldest and largest temples in Bangkok features the famous Reclining Buddha, which is the largest in Thailand measuring more than 150 feet in length.
Most travellers to Bangkok also liked Temple of Dawn (Wat Arun), this temple is considered to be the most famous and photographed temple in Bangkok, which features a soaring 70-meter-high spire decorated with tiny pieces of colored glass and Chinese porcelain.