The tradition that both Ajahn Nitho and Ajahn Brahm are connected to comes from Thailand, and it was Ajahn Chah and his successor Ajahn Liem who were the teachers and mentors for many of the Western monks.

Ajahn Ganha

Ajahn Ganha is a nephew of Ajahn Chah. Some of his teachings have been translated to English:

• Delivery 42
• Delivery 2019
• Monastic Etiquette

Location:
Wat Pah Subthawee
Nakhon Ratchasima 30370, Thailand
https://www.watpahsubthawee.org/
Map link: Wat Pah Subthawee

Ajahn Liem

Ajahn Liem was appointed by Ajahn Chah to take over and be the new leader. Some of his teachings have been translated to English:

• Knowing the world
• The Ways of the Peaceful
• No Worries

Location:
Wat Nong Pah Pong (see below)

Ajahn Chah (1918-1992)

Ajahn Chah was an important factor when Theravada Buddhism spread to the West, because many Westerners took an ordination with him. A lot of his teachings have been translated to English, and can be bought on Amazon. The two biggest collections of teachings in English are for free distribution:

• The Collected Teachings of Ajahn Chah
• Stillness Flowing

Location:
Wat Nong Pah Pong
Ampher Warin Chamrab, Jangwat Ubon Ratchathani 34190, Thailand
http://www.watnongpahpong.org/indexe.php
Map link: Wat Nong Pah Pong
Wikipedia: https://en.wikipedia.org/wiki/Ajahn_Chah