Ajahn Sumedho chose as the topic of his sermon Buddhism Today.
American-born Mr Sumedho's history includes a stint in the US Army as a medical officer and working for the Red Cross in the Peace Corps.
He went to Thailand in 1966 to practise meditation, subsequently ordaining as a monk in the Theravadin tradition.
Theravada Buddhism is one of two principal branches of Buddhist belief, along with Mahayana Buddhism.