Thomas last played for Wales on the tour of Australia in 2007 and will go head to head with the All Blacks skipper Richie McCaw, widely regarded as the world's best number seven.
"Losing Sam was a bit of a blow, especially after how well he played against South Africa," said Wales forwards coach Robin McBryde. "On the back of that Gavin Thomas gets an opportunity. Gavin has been there or thereabouts for a while now.
"He's had a good back end of the season with the Dragons and thoroughly deserves his chance. At his age he's not going to get that many more, so I'm sure he'll be doubly keen to go out there and make a name for himself."
Thomas will be joined in the back row by skipper Ryan Jones and Jonathan Thomas while their Ospreys colleague Andrew Bishop gets the nod at centre ahead of Jonathan Davies after James Hook was ruled out of the tour through injury.
The Wales side has a youthful look to it with teenager Tom Prydie starting on the wing while Tavis Noyle will earn his first cap if he comes off the bench.
"We've got a youngster on the bench in the back row in Rob McCusker and as well as the experienced guys coming back who haven't had an opportunity (like Gavin Thomas). We've got the youngsters coming through who have made an impression and we are keen to see if they can make the next step up," added McBryde.
"There's no better testing ground than New Zealand on their home patch really. It's an opportunity that players have got to grasp. With it not being too far out from the World Cup everyone is keen to make an impression on the coaches and show what they can do."
Wales: 15 Lee Byrne 14 Leigh Halfpenny 13 Andrew Bishop 12 Jamie Roberts 11 Tom Prydie 10 Stephen Jones 9 Mike Phillips 1 Paul James 2 Matthew Rees 3 Adam Jones 4 Bradley Davies 5 Alun Wyn Jones 6 Jonathan Thomas 7 Gavin Thomas 8 Ryan Jones (capt)
Replacements: 16 John Yapp 17 Huw Bennett 18 Deinol Jones 19 Rob McCusker 20 Jonathan Davies 21 Dan Biggar 22 Tavis Noyle