Now, after a series of knee injuries and aborted comebacks, the Netherlands-based footballer is cautiously optimistic his body will hold up for long enough to take him to the game's biggest stage at the World Cup.
The PEC Zwolle captain's perseverance and good form in the Dutch top flight were rewarded when Darren Bazeley recalled him to the All Whites squad last August, nearly six years after his last appearance in a friendly against Ireland.
It signalled a remarkable vote of confidence in a player who was written off repeatedly due to his breakdowns and long absences from the pitch.
Thomas said Bazeley's patience had helped him navigate the bleak periods when sidelined with injury or battling to build momentum at club level.
"There was a long time where I feared my international career was done," he told Reuters.
"I had some calls with Baze and he wanted to let me know the door was always open. I was always really grateful for those calls with them.
"I didn't expect I would be able to come back to the national team. And now that I'm able to be back and amongst these boys and playing these games, it's brilliant."
Thomas has returned to his home nation for friendlies against Finland and Chile, New Zealand's last warmups on home soil before the June 11-July 19 World Cup in North America, the nation's first appearance at the finals since 2010.
The road back to the All Whites has not been entirely smooth, with Thomas missing friendlies against Ecuador and Colombia in the United States during the last international window in November while under an injury cloud.
At the time, Dutch media reported Zwolle manager Henry van der Vegt was unhappy with him risking his fitness while on All Whites duty.
Thomas, however, said he had been misquoted.
The balance of playing for club and country is often a delicate one, but Thomas said he would not miss any New Zealand game lightly.
"It's always tough. If you're 100% fit then you go away (on international duty) and you get on the end of a bad tackle, and you do a ligament or something, everyone's going to think you shouldn't have gone," he said.
"It's a privilege to come back and play for the national team. There's always ups and downs, and there's always things that people are going to say.
"But whenever I'm fit, I'm always going to be available."
Once barely training to try to preserve his body, Thomas said he was now able to put in serious shifts between match-days and it was paying off.
It bodes well for his chances of nailing down a spot in Bazeley's World Cup squad - but Thomas is naturally taking nothing for granted.
"There's so many good players performing well for their clubs. If players aren't (performing), Baze has got other options," he said.
"It can't be about relaxing and thinking we're going to the World Cup 100%."