Buddhism
The most commonly practiced form of Buddhism is Mahayana Buddhism. The word Mahayana translates from the Sanskrit as "great raft". It is believed to be a vehicle that carries large numbers of people toward enlightenment.
Theravada.
In most countries of the world. However, the countries where Theravada Buddhism is the major religion include Sri Lanka, Thailand, Burma, and Cambodia.
Theravada, the "Doctrine of the Elders," is the school of Buddhism that draws its scriptural inspiration from the Tipitaka, or Pali canon, which scholars generally agree contains the earliest surviving record of the Buddha's teachings. For many centuries, Theravada has been the predominant religion of continental Southeast Asia (Thailand, Myanmar/Burma, Cambodia, and Laos) and Sri Lanka. Today Theravada Buddhists number well over 100 million worldwide.
Thailand is predominantly Buddhist, with about 5% of the populace practicing Islam.Buddism.Buddhism
The most common type of Buddhism is Theravada Buddhism. It was founded in India, and is the oldest surviving Buddhist school. It is practiced by an estimated 100 million people worldwide today.
If you are referring to Sects, there are numerous sects in Buddhism. Probably the most famous are Mahayana, Theravada, and Zen.
Buddhism is the most practiced religion in Laos, followed by a significant portion of the population. There are also smaller communities of Christians and followers of traditional animist beliefs in the country.
Buddhism and Shinto
Taoism, Buddhism, Islam, Catholicism, Protestantism
This is too complex to answer in full here, but please refer to this excellent website which has a detailed discussion of the schools and lineages:http://www.buddhanet.net/e-learning/history/schools.htmThe three branches of Buddhism are Mahayana Buddhism, Vajrayana Buddhism, and Theravada Buddhism.