To obtain the guest keycard in Sons of the Forest, you will need to have the maintenance keycard. First, travel to the 3D printer bunker located north of the rope gun cave. Once you enter the bunker, take the first left turn and proceed down the corridor. Then, take a right to find a double door and enter the gym. Take the first left and continue straight past the reception desk into a large room with two winding staircases. Go up the stairs and keep moving forward past the pool until you reach the room ahead.

In this room, there is a guitar on the bar counter that you can pick up if you want a new melee weapon. Walk through the bar area and into the lounge area to find the guest keycard on the table of the fourth lounge on the right.

Other notable items that can be found in this bunker include a chainsaw, tracksuit, emails, Mr. Puffy Will, and shotgun rail.