Surasak ''Boy'' Suwannachot, 26, betrayed no emotion as a judge told him there was convincing evidence he stabbed Mrs Smith, 60, during the Phuket robbery attempt on June 20.
Khun Surasak tried to grab Ms Smith's shoulder bag as she and another travel agent from Perth, Tammy Lee Lynn, 42, were walking home after dinner to the Katathani Phuket Beach Resort at Kata Noi, one of Phuket's most quiet beaches.
Mrs Smith would not let go of the bag so Khun Surasak stabbed her above the heart. The two women walked on for a few steps before Mrs Smith collapsed, dying.
In contrast to Khun Surasak, Surin Taptong, 37, who allegedly rode the getaway motorcycle for the pair, was at one stage in tears and at first denied any knowledge of the robbery.
After Khun Surin's denial, the judge warned him and his lawyer that telling lies to the court could lead to a heavier sentence.
After saying initially that he did not know that Khun Surasak was planning a robbery, Khun Surin watched a screening of the security camera footage, then also confessed.
The media was asked to leave the court briefly as Khun Surin vacillated between pleading guilty or innocent.
The hearing was continuing this afternoon.