Athletic used their game in hand to full effect by racking up four tries and a bonus point, leaving them four points clear of closest rivals Builth Wells and Loughor.
At the other end of the table, bottom club Gorseinon upset mid-table Pencoed 27-15 and Gorseinon now trail second-bottom Penclawdd by just one point after this three try victory.
Glynneath went ahead of Tondu into second spot in Division Three South West after their 22-10 victory over Maesteg Celtic.
Ystalyfera also move into second in their respective division, as they hit seven tries in a 39-20 win at Neath Athletic in Division Four South West, as do Talywain in Division Five East by beating RTB Ebbw Vale 36-8.
Cilfynydd are the new leaders of Division Five South East after they beat fourth-place Deri 31-28 in a match where both teams recorded bonus points.
