The 21-year-old helped the Bees to the League Two title as a virtual ever-present in his season-long loan spell at Griffin Park.
But with Marcus Hahnemann having left the Royals, Hamer is now able to challenge Adam Federici for the number one shirt at the Madejski.
"I've got things sorted with my agent now, so I'm going to sign a two-year deal with Reading," he told the Hounslow Chronicle.
"They want me to challenge next year. I've been told I'm going to be fighting for the number one spot, so I'd only probably go on loan if I was third choice.
"Fed is in front of me. He's played at a higher level, but I'm going to get my head down in pre-season and give it a go."