I'm another one who doesn't see the ohhh in Bali. It's busy and crowded. I suppose a super nice/expensive resort might be different, but you can get that anywhere. Last year, I spend a few nights in Ubud and found it meh. I loved the little villa we stayed in in the rice fields--we had our own small pool that was lovely.

I'd chose BKK over Tokyo for a few days at that time of the year. Tokyo will be cold and that means a lot more luggage to haul around. I like Singapore, but I think Bangkok is much, much more interesting.