Much of the Thai forest tradition's presence in the English-speaking world traces to a single teacher, Ajahn Chah, whose monastery in northeastern Thailand trained a number of Western students from the 1960s and 1970s onward, several of whom, including the American-born Ajahn Sumedho, were themselves later recognised as ajahn and sent or invited to establish branch monasteries in the United Kingdom, the United States and elsewhere, founding institutions such as Chithurst and Amaravati in England that now train their own further generations of Western-born monks entirely outside Thailand.
These branch monasteries have generally kept the forest tradition's strict monastic discipline and its emphasis on meditation intact while adapting practical details, food donation logistics, climate and legal status, to operate in countries with no existing culture of lay almsgiving to monks, so an ajahn trained and recognised at one of these Western branch monasteries today holds the same seniority-based title as a monk trained in rural Thailand, even though the surrounding society supporting the monastery looks nothing like the one the tradition originally developed within.
The same Thai forest lineage established a further branch monastery in the United States, Abhayagiri in northern California, founded in 1996 by Ajahn Pasanno and Ajahn Amaro after their own training under Ajahn Chah's successors in Thailand and England, giving the lineage a specifically North American training centre alongside its earlier English foundations and extending the same seniority-based ajahn title to monastics trained and ordained entirely on the American west coast, a further step in the lineage's spread well beyond the rural Thailand where it began.