NEWTOWN slipped back to third from bottom after a disappointing second half showing at Richmond Park.
Unbeaten in their previous three outings, the Robins more than held their own in the first period with a resolute display.
But they returned from West Wales empty-handed with strikes from Kaid Mohamed and Danny Thomas settling the issue after the break as the hosts ran out deserving victors.
Newtown had restricted Carmarthen to few chances in the first period, the best of which saw Kris Thomas rattle the post on the half hour.
Mattie Lewis spurned one good chance for the Mid Wales men, the front- runner firing wide when he could have done better, while home stopper Neil Thomas punched clear a couple of times under pressure from Rob Williams.
But the visitors, despite a battling display from Gareth Hughes in midfield, were unable to build on their first half display as they found themselves breached 10 minutes into the second period.
Right-back Terry Evans overlapped down the flank before picking out Craig Lima at the far post with his cross.
A goalmouth scramble ensued following the knockdown, with Mohamed eventually seizing on the loose ball to fire home.
And the encounter was effectively wrapped up with the visitors falling further behind on 67 minutes as Paul Fowler set up Danny Thomas to fire home.
Newtown's disappointing second half continued when they were reduced to 10 men moments later after defender Brian Showdery was sent off for his second booking.