Barry Davies darted over five minutes into injury time to clinch a precious bonus point as the Scarlets roared back into second place in the Magners League. Dafydd James, Deacon Manu and Darren Daniel also crossed as the Scarlets found their spark to out-score the European champions four tries to nil.
Jeremy Manning kicked all of Munster's points as the game hung on a knife-edge at 15-12 with just five minutes remaining. But late strikes by Daniel and Davies ensured the Scarlets moved to within five points of league leaders Ulster - but with two games in hand.
Both Llanelli, lead by flanker James Bater, and Munster fielded much-changed sides due to international commitments but it was Test veteran Dafydd James who got the Scarlets on their way. Ceiron Thomas, standing in for Wales skipper Stephen Jones, opened a hole with his footwork, stepping between two defenders before off-loading to James who surged over from 25 yards out.
Manning reduced Llanelli's lead to 10-9 at the break but Manu barged his way over from close range two minutes into the second-half to leave daylight between the sides. However, Thomas was off-target with the boot and the Scarlets were at risk of throwing away a game they controlled throughout after Manning reduced the lead to 15-12.
Manning missed a drop goal and a penalty before Matthew Watkins pounced on a Munster mistake in midfield to create the winning try. Trevor Halstead spilled possession under Regan King's challenge, Watkins scooped up possession to release speedster Daniel who raced past the clutches of Manning.
A bonus point looked to eluded the Scarlets until they punished another Munster error, James driving forward before Davies darted over in the corner on 85 minutes.
Llanelli Scarlets: Tries - D James, D Manu, D Daniel, B Davies. Con - C Thomas. Pen - C Thomas.
Munster: Pens - J Manning (3). Drop G - J Manning.
Referee: Kelvin Deaker (New Zealand).