Corus recorded their fifth straight win with a 29-22 result in an entertaining, seven-try match against Kidwelly. Lewis scored two tries and kicked nine points as the league leaders kept their noses ahead of Dunvant, who made it four out of four with an impressive 30-3 win at Carmarthen Athletic.
Gorseinon were the only other team who went into Saturday's games with an unbeaten record, but Bridgend Athletic took care of that with a well-deserved 20-13 win at home.
Seven Sisters fullback Kevin Lewis kicked four penalty goals as his side edged past Felinfoel 22-14 to record their second victory of the season. Loughor fullback Lee Davis matched Lewis' feat, his four goals providing all of his side's points in their 12-10 win at winless Banwen, while Maesteg Quins beat Tonmawr 17-3 and Pontyberem accounted for Mumbles 20-12.
Trimsaran and Haverfordwest are locked together at the top of Division 3 West, although Haverfordwest did it the hard way with an 18-16 win at winless Lampeter. Trimsaran cruised to a comfortable 27-3 victory over Newcastle Emlyn.
At the wrong end of the table, Tumble (35-19 losers to Aberystwyth), Lampeter and Hendy (18-5 losers to Tenby) are still looking to lose the duck's egg beside their names.
In Division 4 West, Pontarddulais continue on their merry way at the top after a 37-6 win at Cardigan, while second-placed Neyland were held to a 13-all draw at Milford. There was another draw in the division, with bottom-placed Llandybie earning their first point of the season courtesy of a 6-all deadlock at home to mid-table Ammanford.
Llanybydder are alone at the top of Division 5 West after their fifth straight victory - a 49-0 mauling of Pontyates - although Burry Port also retained unbeaten with a gritty 22-18 victory at Tycroes.
Pontyates are one of three sides still looking for their first win. The two Saints - David and Clears - are holding up the table after St Davids fans had to sit through a 57-6 hammering at the hands of Gowerton and St Clears fell 16-36 at home to a Llangwm side celebrating their first win of the season.
Wales reached their first semi-final since 2013 in the opening round of this season's HSBC World Rugby Sevens Series in Dubai. WRU TV's Graeme Gillespie recaps on what proved to be an eventful tournament
Wales and Ospreys back row James King, who came through the North Wales age grade system, nominated North Wales Regional Community Rugby Manager Marc Roberts, in the WRU's 'Diolch' initiative where squad players thanked those who played a part in their rise to the top.
Beating Merthyr has boosted Carmarthen Quins hopes of reaching a top eight spot in the Principality Premiership. Quins captain Haydn Pugh is delighted with his team's progress and is determined that everyone from the Under 6s through to the senior team, enjoys the ride.
When the Wales squad were asked to nominate individuals who played a big part in their early playing days, Wales and Dragons full back and wing Hallam Amos thought of his former Monmouth School rugby coach John Bevan.
Sam Cross and Luke Treharne have been named as co-captains of the Wales Sevens side as head coach Gareth Williams names his 12-man squad to play in the first leg of the HSBC World Series in Dubai next weekend.
Bedwas head coach Steve Law and players Nicky Griffiths and Alun Rees extol the virtues of the close knit club as they prepare to host third place RGC 1404 - who are one place head of them on the Principality Premiership points table - on Saturday.
Many of the Wales squad have said Diolch (thank you) to someone who played an important part in their early playing days by nominating them to be invited to the Wales v South Africa match. One person, Gowerton Comprehensive geography teacher Mr Dean Mason was nominated by two of his former pupils, Dan Biggar and Sam Davies.
The second WRU disability rugby pilot has been delivered, this time in Caerphilly schools, culminating in a festival at the Caerphilly Centre of Sporting Excellence, Ystrad Mynach tomorrow. Plans are in place to set up a Disability Rugby Club in Newbridge to provide long-term playing opportunities.
WRU TV: Hear from inside the Wales camp as Neil Jenkins discusses this weekend's clash with South Africa and how the squad are looking to put in a strong performance to round of the 2016 Under Armour Series