Speaking after a 3-0 win at Cheltenham Town, the Bolton boss briefly addressed the offer from the Championship side, which is understood to be worth £1million.
Thomason came off the bench in the second half at Whaddon Road and his future is expected to be decided early this week.
“We have had a significant bid for him but it is as far as it goes, for now,” Evatt said.
“We have received an offer and there are conversations happening behind the scenes but that is all I can really say right now.
“It should be resolved over the next 48 hours”
Wanderers strolled to their second successive league win and now top the embryonic table after two goals from Dion Charles, either side of an own goal from Liam Smith.
“It was a very good performance,” Evatt said. “Players had the right energy and attitude right from the start. You can see a lot of the principles we have worked on coming to fruition.
“Even in tight positions we managed to break their press at will, waited for one of their players to jump and then exploit the space behind them.
“I thought it was a really good performance but that’s all, it’s done, we park that now and prepare for two really big home games.”
Charles – who became the first Bolton player in two decades to top 20 goals last season – opened his account with two neat finishes. The Northern Ireland international caused all manner of problems for Cheltenham but was withdrawn in the second half to save him for Tuesday’s game against Fleetwood.
“I thought him and Victor Adeboyejo were absolutely outstanding,” the manager said. “The way they linked up, the way we played into them, was excellent. I was delighted with Cameron and Dan when they came on as well, some of the connections and combinations with Paris and Carlos show what they are going to offer as well. It is an exciting group to work with.”
Wanderers now go back to the Toughsheet Stadium for back-to-back home games against Fleetwood and Wigan Athletic and with Evatt instructing his players to keep their feet firmly on the ground.
“It is just a start – the weight of expectation is with us this season and so it was important to get a good start,” he said. “Three wins and three clean sheets is exactly that.
“But I still think there is much more to come from this group of players, they are learning and developing all the time. There is more there. It is a solid start but there are two big home games coming up, Fleetwood first and then we’ll talk about the derby.”