The Thai Forest Tradition

Thaiforestwisdom.org; Dhr. Seven, Amber Larson, Pat Macpherson (eds.), Wisdom Quarterly

Buddhism is estimated to be some 2,600 years old. As it spread, different schools arose. There are now essentially at least three Buddhisms based on different scriptural canons.

There is Theravāda Buddhism based on the Pali language canon, the East Asian tradition (Mahayana) centered on the Chinese canon, and the Tibetan tradition (Vajrayana) centered on the Tibetan canon [Reference: Buddhist Religions, a Historical Introduction, Robinson, Johnson, and Thanissaro (eds.), 5th edition, pg. xxi]. For general background reference material on Buddhism, see:

• Ven. Shravasti Dhammika's Guide To Buddhism A to Z (with Alphabetical Index, Subject Index, and reference Abbreviations)
• Wikipedia's Glossary of Buddhism 
• The Encyclopedia of Buddhism available via A Handful of Leaves

The oldest complete set of scriptures is the Pali canon. The Thai Forest Tradition arose at the end of the 19th century as a deliberate attempt to focus on the practice of meditation as described in these early sutras. [Some therefore say it is an illegitimate sect, invented by a Thai royal out of thin air, but it has produced many great meditating monks.]
 

It is relatively new and, perhaps, also very old as  well. There are numerous discussions of this tradition online. A great place to start is The Customs of the Noble Ones by Ven. Thanissaro (from Access to Insight). Here are a few more favorites:

• Thai Forest Tradition (Wikipedia) 
• Forest Tradition (Vimutti Buddhist Monastery) 
• Thai Forest Tradition (Forest Dhamma Monastery) 
• Significance of the Forest Tradition (forestSangha) 
• Thai Forest Tradition (Abayagiri) 
• About the Thai Forest Tradition (Thai Forest Dhamma) 
• Kammatthana (kammatthana.com) 
• The Mindful Way – The Buddhist Forest Tradition (YouTube - 1979 BBC Ajahn Chah documentary - 19:01) 
• Our Life is Like Our Breath (YouTube - life at Ajahn Chah's Wat Nong Pa Pong - 44:06) 
• The Thai Buddhist Forest: Thudong (YouTube - beautiful slide show with excellent music - 1:10:21)

An excellent account of an exemplary dhutanga or thudong monk's life was written by Ven. Khantipalo—With Robes and Bowl, Glimpses of the Thudong Bhikkhu Life. It can be read online or downloaded: HTML (via Access to Insight), PDF (via Buddhanet.net's Buddhist eLibrary )