Wales know they let the Wallabies off the hook, twice, before going down 29-23 in injury time, but Thomas insists that's all the motivation they need to finish the job second time around.
He said, "It won't be hard to pick ourselves up for this one. The only thing that is going to help the pain of that defeat is by winning this week.
"I'd be lying if I said we weren't all absolutely gutted with the result, but as heartbreaking as it was, we have to bounce back and lift ourselves up from this loss. We're representing our country again so that will help us all focus on trying again.
"It's hard to put the disappointment into words when you put so much effort into a game and give a hundred per cent, only to lose on the last play of the game. As players you strive to do your best and hope you get rewarded for that.
"Everyone gave their all but to lose at the end like that is a very bitter pill to swallow, but now we have to put it behind us and look at the second Test. That's what counts now."
The Welsh defence will come under scrutiny with Stephen Larkham returning to pull the home side's strings. Experienced forwards Dan
Vickerman and George Smith also start as the Wallabies look to sharpen their claws.
Yet Thomas said, "We've been working a lot with Rowland Phillips on our blitz defence and it worked really well in the first 20 minutes on Saturday.
"We shot down their space and didn't give them time on the ball. That forced them into errors and we took our chances very well. It will be even tougher this weekend, but we know we can improve."
Wales: Gareth Thomas (Capt); Chris Czekaj, Jamie Robinson, Sonny Parker, Aled Brew; James Hook, Mike Phillips; Iestyn Thomas, Mefin Davies, Ceri Jones, Michael Owen, Rob Sidoli, Colin Charvis, Gavin Thomas, Jonathan Thomas
Replacements: Chris Horsman, Richard Hibbard, Scott Morgan, Robin Sowden-Taylor, Andy Williams, Ceri Sweeney, Gavin Henson
Australia: J Huxley, D Ioane, S Mortlock (Capt), A Ashley-Cooper, D Mitchell; S Larkham, M Giteau; W Palu, G Smith, R Elsom, D Vickerman, N Sharpe, G Shepherdson, S Moore, B Robinson
Replacements: A Freier, M Dunning, M Chisholm, S Hoiles, P Waugh, G Gregan, M Gerrard