Aiseai Havili scored two of his side’s six tries while Gareth Bowen was also to the fore.
Bowen had scored all 10 points from a converted try and a penalty as the Llanelli based side raced to an early lead and the fly half put also up a well placed cross field kick for Havili to collect his first touchdown, while the Borders could only reply with a Charlie Hore penalty. Before the interval the home side had increased their lead when Dafydd Jones crossed for their third try.
The Borders did hit back straight after the break when Scotland wing Simon
Danielli slipped past some weak defence to cross in the corner, but the respite
was only short-lived. Tal Selly secured the bonus point for the Scarlets and although Borders struck back with a close-range effort from wing Nikki Walker, it was virtual one-way traffic after that.
The outstanding Watkins danced past a string of defenders for a deserved solo score on 58 minutes, before replacement scrum-half Dwayne Peel put Havili away for his second.
The Borders battled to the end and claimed a third try through second row Colin Stewart but they were unable to claim an elusive bonus point.