Bus is the most used transportation means by Thai people in Thailand. There are two kinds of buses run in Thailand. One is air-conditioned, the other is non-air conditioned bus. The non-air conditioned buses are operated by the government. They are cheaper and slower. The air-conditioned ones run by government as well as private companies. They are more comfortable, faster and price is higher. There are some long distance buses called “VIP” or “sleeper” bus. They only have 30-40 seats and have more legroom for the passengers.
Bus can take you to almost anywhere you want to go in this country. The price is very cheap especially for the government-run non-air conditioned ones. The VIP Buses is more expensive than normal buses but they offer more comfortable seat, one or more meals and a bottle of water. Sometimes, TV shows or movies are broadcasted on board, but only in Thai. There is no luggage limitation for the bus and there is not an extra charge to extra weight. If you will visit an island, you also can choose a bus+ ferry ticket. Each city has its own bus terminals. You can go directly to the terminals to buy the tickets where you can compare the price of tickets from deferent companies or find the schedule that most suitable to you. There are three major bus terminals in Bangkok and each has its own region destinations. Mochit, the largest terminal in Bangkok, offers most departures to the north of Thailand. Ekkamai offers buses to the east places of the country and Sai Tai Mai offers departures to the south. Mochi is nearby Chatuchak Weekend Market which is about half hour to go from downtown by car. The others are also located not near from the downtown and you have to take a taxi, tuk tuk or songthaew to reacn them.
There are direct international buses to Siem Reap, the nearest city of Angkor Wat and Phnom Penh in Cambodia from Bus Terminal-Mochit. When crossing the border of the two countries, you need get off the bus and get your visa by yourself then climb back into the bus and continue your journey. The fastest bus takes around 9 hours from Bangkok to Siem Reap. The number of seats is limited so it is better to book in advance.