Neath were crowned Welsh Premiership champions for a third successive year on Saturday when nearest rivals Newport lost at home to Pontypridd.
Neath have secured a record third title in a row
Newport needed to win and score 15 tries to deny the Welsh All Blacks the title.
But the defeat, and Ebbw Vale's win over Llanelli, means the Black and Ambers finish the season in third.
Neath will be presented the Premiership trophy at a tribute game to Brian Williams at Narberth RFC on Sunday.
Trouble is brewing over promotion to the Premiership, though, with both Division One East winners Beddau and Division One West champions Bonymaen to be denied elevation to the higher league.
The Welsh Rugby Union have told both clubs that they will not be promoted because their grounds do not meet the necessary standard.
Both clubs are considering calling for an Extraordinary General Meeting to have the decision overturned.
"It's disgusting, we weren't given the criteria until mid-way through the season, but we can get everything in place this summer," Beddau coach Brett Davey told the Wales on Sunday newspaper.
"The WRU are hypocrites. They talk about clubs improving, but what's the point when you can't get promoted to the top division?
"We've worked hard all season to beat teams who are paying big money, and we deserve our place with the big boys.
"If we don't go up I'll never coach in Wales again. I'm sick of it."