In 2012, he was appointed head coach of the Manu Samoa team, on a four-year contract until after the 2015 Rugby World Cup.
[2] His first match in charge came on 5 June 2012 during the 2012 IRB Pacific Nations Cup, where Betham led Samoa to a 20–18 victory over Tonga.
[5] In November 2013, Bethan led Samoa to a white wash end-of-year tour, losing to Ireland 40–9, and Georgia 16–15.
[8] On 19 October 2015, Betham stood down as Samoan head coach following a disappointing 2015 Rugby World Cup.
Samoa who were largely expected to finish second in their group, went on to lose to South Africa 46–6, Japan 26–5, a record defeat, and Scotland 33–36.