About 120 people filled the Wingatui grandstand to watch the contenders go head-to-head on Saturday after a qualifying day on Friday.
After tackling farming challenges ranging from offal and tractors to bees and business sheets, Mr Thomas said he was feeling tired, but excited.
"It was a big weekend and it’s still still a bit surreal, still sinking in."
It was the third time the Waitane young farmers member had competed for the regional title, and he felt grateful for the win.
Going in with no expectations on himself had been the attitude that made the weekend go smoothly and without stress, he said.
"I think the hardest part was managing myself just to keep calm, just to take a breath and have a crack.
"You’re not gonna win everything, but you might learn something."
It was the attitude he would take to the grand finals in Hamilton in July, which he was looking forward to.
Events manager and contest specialist Nick Kennedy said it was important to test young farmers across several different challenges.
The Otago Southland region was one of their strongest when it came to participation, so "a gauntlet of farm skills" was needed to whittle it down to a single finalist.
"We’re testing them in all areas.
"They have to work in all these facets to be the best farmer in New Zealand."
One highlight was the agri-skills section, which pitted the eight regional finalists against one another in a race to be the fastest farmer.
Mr Kennedy said contenders placed themselves in the shoes of a farmer who had witnessed an accident on their way to work.
A variety of themed obstacles stood in their way including taking care of a horse, tending to casualties, handling a fallen tree and even a damaged trough.
Mr Kennedy said over two days competitors had also completed 18 smaller modules on topics including offal, bees, shearing, tractor programming, human relations and balancing business sheets.
The regional finals concluded in a quiz with university-level questions about farming, before Mr Thomas was announced as the winner of the competition on Saturday evening.
Mr Kennedy said Mr Thomas had "definitely put the hours in" and was the most competent all-rounder.