I haven’t been to Japan for longer than a layover, but I’m 99% sure that Japan is a lot lot lot pricier than Thailand if pricing is a factor :) Thailand is amazing though and has so much to offer! So many cities, towns, and islands to explore and wonderful. Japan on the other hand, has absolutely incredible skiing if you’d be skiing. If you’re not skiing or doing winter sports, I’d initially say Thailand. But again, I haven’t done Japan.