Thompson stressed that the Tigers would not go down the road of 'short-term fixes' as they embark on their second journey into the top-flight in six seasons.
He told the Hull Daily Mail: "We want players who are with us for the long-term, not just a short-term pay cheque where if it goes wrong it'll be 'Thanks very much' and we're back to square one.
"Short-term fixes will get you into trouble in the Premier League. It's ensuring that whatever you do, it adds quality to the squad going forward.
"I think we'll be looking at perhaps five or six coming in. Maybe it will be slightly more, maybe slightly less, but it would be somewhere around that.
"I'd hope to see the first new signings going through by the middle of June, two or three weeks away.
"We might work quicker or we might have to wait on certain players but transfer deals don't just happen.
"Even when we're talking to players now, they're keen to keep their options open. You're jostling for position at the moment and seeing where you end up standing.
"Players become available all the time, they come into clubs, they drop out. Some clubs want to sell, some don't want to sell.
"The reality is that the international window doesn't open until the middle of June and the home window doesn't open until the start of July, so it's really about being prepared. Steve (Bruce, manager) is away on holiday but we speak every day."