Scarlets finished fifth in the league last year and as a result just missed out on the play-off places but Thomas is hopeful that despite the absence of numerous Welsh internationals, they put it right this season.
History is with Munster, who have won their last three matches in all competitions and they have lost just once at home since October 2011.
And at Musgrave Park their record is all the more impressive, having won their last 15 matches, while Munster are unbeaten in their last 15 matches with the Scarlets.
But Thomas is convinced that his side can upset the applecart in Ireland - claiming it will be crucial to their end-of-season ambitions.
He said: "The next couple of weeks are massive concerning our ambitions of getting to the Pro12 play-offs.
"If we can get two wins in the next couple of weeks, it puts us in a really strong position going into the Christmas games and the New Year.
"It's a tough place to go, but all the away games in Ireland are tough. We have to match them physically and take our opportunities. It's a massive couple of weeks for the squad."
There's a return to regional action for Morgan Stoddart at full-back as Liam Williams is called up to Wales to replace his injured Scarlets team-mate George North.
Andy Fenby is on the wing with Nick Reynolds in for the injured Kristian Phillips while Gareth Davies joins Thomas in the half-backs.
Kirby Myhill and Samson Lee have been released back from Wales' training squad this weekend, adding some youthful power and energy to the Scarlets bench, while South African signing George Earle moves from the second row to cover for the number of international call-ups for Scarlets back-row players in addition to injuries.
Munster have made six changes to the side that overcame Cardiff Blues last time out with Niall Ronan back after almost two months out with injury to replace Sean Dougall at openside flanker.
Paddy Butler comes in for Tommy O'Donnell at No.8 and Ian Keatley moves back to fly-half while Wian du Preez starts ahead of Marcus Horan at prop, Ian Nagle partners Billy Holland in the second row and James Downey is back as centre partner for Casey Laulala.
Ronan said "I'm really looking forward to getting back out there.
"We've concentrated on scrums and lineouts this week and if we can match them in those areas then I think we'll have a good chance.
"We're expecting a very tough game this weekend. I think the Welsh teams are very physical. We have to match them in the physical side - in the pack. If we don't do that then we'll be under serious pressure."
At Musgrave Park , 5.15pm.
Referee: Laurent Cardona (FFR, 1st competition game)
Assistant Referees: M Patton, Eanna O'Dowd (both IRFU)
Citing Commissioner: John West (IRFU)
TMO: Seamus Flannery (IRFU)
Live on TG4 and S4C