The win takes Neath to second on the table behind unbeaten Bridgend, who beat Cross Keys 23-11 courtesy of a try double to No 8 Dean Fitzgerald.
Former table-toppers Pontypridd crashed to their first loss of the season at home to Llanelli, despite scoring in only the third minute through winger Chris Clayton.
Pontypridd led 16-5 at the break but had no answer to a fired-up Llanelli side, who scored three tries in a second half marred by several fights and four yellow cards - two for each side.
Newport stayed in touch with the leaders with their fifth win of the season - a 23-14 victory over Maesteg at Rodney Parade. Richard Payne and Sam Waldron scored tries and outside-half Aled Thomas added 13 points with the boot.
Glamorgan's backrow pair of Marcus Leach and Richard Thomas both scored tries in Wanderers' 22-17 win over Llandovery, while Aberavon winger Daran Griffiths grabbed his 115th career League try in the Wizards' 21-3 victory at Pontypool.
Swansea recorded their first victory of the season - a surprise 39-27 win at Bedwas.
Results: Bedwas 27 Swansea 39, Bridgend 23 Cross Keys 11, Carmarthen Quins 19 Cardiff 23, Ebbw Vale 29 Neath 47, Glamorgan Wanderers 22 Llandovery 17, Newport 23 Maesteg 14, Pontypool 3 Aberavon 21, Pontypridd 19 Llanelli 29.