Welcome and thank you for allowing me to assist you! This is a problem with the drain tube in the right front corner of the sun roof. It has either become disconnected, is clogged, or has a break/crack in it. Now in most cases you can just de trim that area around the headliner and pull the headliner down just enough to inspect the drain tube. You will remove the right sun visor, the front A pillar trim, and the trim around the seat belt retractor. Pull the weather strip away from the body. You should then be able to pull the headliner down and check that tube. The tube simply presses onto the right front corner of the sun roof frame. If you have an air compressor, you may be able to clear a clog in the tube by blowing compressed air into the tube.
I hope this information helps, and let me know if you need further assistance with this.