In 1971 he was appointed Secretary General of the South Pacific Commission, a role he held for four years.

In World War II he was part of the Western Samoa Defence Force.

He was appointed an OBE in the 1962 New Year Honours and remained in the cabinet until the 1970 elections, when Tupua Tamasese replaced Fiame Mata'afa as Prime Minister.

After a tie in the first round of voting, his opponent Oala Oala-Rarua withdrew from the contest, allowing Betham to win.

[5][6] He served as Secretary General until 1975,[2] and in 1976 was appointed High Commissioner of Western Samoa to New Zealand, a role he held until 1980.