Thompson will run out in Manly colours for the first time in Saturday night's trial against Sydney Roosters on the Central Coast.

The 29-year-old back-rower was signed to the Dragons for 2018 but a two-year contract offer from Sea Eagles coach Trent Barrett was too good to refuse as he prepares to enter the twilight of his career.

Thompson said the security of the extra year offered by Manly prompted him to seek a release.

Asked if he felt like he was unwanted at the Dragons, Thompson said: "I thought I deserved that extra year for what I did on the field but I understood their position.

"I've been around footy long enough. They've got some great young guys coming through.

"We were honest throughout all the conversations. I respect their decision.

"Do I agree with it? Probably not. But that's footy and we left on good terms."

The central NSW product was signed by Manly despite the prospect of sanctions for alleged salary cap breaches hanging over the club.

Thompson said it was hard to uproot his family and move to his third club in six seasons but the security of a multi-year deal gave him piece of mind.

"To be totally honest, Manly offered me another year on my contract," Thompson said.

"I grew up supporting Manly and I like the squad they've got here and what they're doing. I wanted to be a part of it.

"It gave me a bit of security, I'm not young anymore, I'll take what I can get."

Australian Associated Press