2 year old moving to bed

My 2 year old was climbing out of his crib, so we moved him to his floor bed 6 days ago. He used to sleep great until he started being able to escape the crib and now bed. He’s able to open the door and walk out of his room. We remind him to go back to bed but he’s been getting up at 4:30-5:30 daily.

Besides a baby gate, are there any other options to ensure he doesn’t get out of his room in the middle of the night? I’m so nervous I won’t hear him. Lastnight we used the safety knob but 5:30 am came and he opened it no problem.