Wingers Dion Thomas and Jack Tremlett each scored a try double as fourth-placed Whitland smashed a weakened Narberth side 47-0 at the Lewis Lloyd Ground on Saturday.
Bonymaen need only four points from their final four games to guarantee a title win, and that doesn't look like a problem after their six-try effort against Llangennech. Flankers Ewan Hopkins (two) and David Absolam scored half the tries between them, and outside-half Gareth James supplied a handy 19 points.
Second-placed Beddau jogged to a 48-12 win over Llanharan, thanks partly to a try double from winger Dan Wyatt, but they have only one match left this season - a trip to struggling Waunarlwydd - and a top-three spot seems to be their lot.
Caerphilly's first season below the Premiership continues to be a frustrating one, and their normally reliable fortress at Virginia Park was gate-crashed by Newbridge on Saturday.
Rhys Reynolds scored two tries for the third-placed visitors, and the convincing 22-3 win cements the Cheesemen's position in the bottom half of the table.
Rob Lloyd converted four of Builth Wells' five tries in a 33-23 win at UWIC, but the result wasn't enough to move the 12th-placed club above the Students in the table.
Blackwood returned from struggling Fleur de Lys with a 22-12 win, and Cwmllynfell were far too good at home to Waunarlwydd, winning 44-7. The home team's bench did most of the damage, with replacements Paul Skilton, Neil Thomas and Lee Davies all among the try-scorers.
Ystrad Rhondda's chances of climbing off the bottom look virtually impossible after their 24-14 loss at Merthyr. Jason Price scored two tries for the home side, and Ystrad now need to win all four of their remaining matches to have any chance of avoiding the dreaded last-place spot.