With Wales now building towards the next World Cup in four years time, Evans has decided now is an opportune time to call it a day.
"With a new coaching set-up coming in, and a lot of girls deciding to take a break from the game, that means the focus will be on a much younger squad and their main aim I would think is a re-building phase.
"I have been involved in a lot of rebuilding processes and I'd rather finish at the top than linger on and be there for the sake of being there," she added.
"It's been absolutely amazing to represent Wales 87 times and score 64 tries - that's just brilliant and I've travelled the world. I've played in world cups and it's been my life and enriched my life and I've just got the most amazing memories."
Thomas said: "I didn't want to be considered for selection this year as I'm looking to take a break from things as I've been doing it for over 10 years."
Skipper Mellissa Berry, with 85 caps next to her name, has retired from international rugby while her back row partner Jamie Kift is another who is taking time out from the game while flanker Catrina Nicholas and second row Gemma Hallett are unavailable for selection as they are travelling the world.