Early in your message you say the last week of November, and then later you mention “late December,” so I’m not sure which it is. But if it’s late November, I think Italy could be a great option, as the weather there is still quite nice, at least in the south. You could go to Venice for a day or two and then Florence and Rome, and then maybe spend 5 or so days in Sorrento. I spent 5 days in Sorrento in mid November two years ago and the weather was very nice, even if it wasn’t warm enough to sit on the beach.
Say Hydrated – This is a no-brainer and one of the most significant challenges for me. I never drink enough water, but it was hot this week in Florida when we were at Disney, and I could tell such a difference in how I felt when I was hydrated. I felt like it made it easier to stay strong and stick to eating low carb/keto as it helps to quench false hunger.
If you do want to go to Thailand then Bangkok is the obvious starting point and it’s a wonderful city. You also want to visit Ayutthaya, which you can do on a day trip but it’s better to stay a few days. Chiang Mai is the highlight of the north, partly because it’s insanely cheap and the weather is a bit cooler than Bangkok. Luang Prabang is another town not to miss and it’s fun for at least a few days. Don’t bother spending much time in Vientiane though.
Sunny SoCal may be beautiful all year-round, but the more-than-mild temperatures of November make it an even more stellar choice for those hoping for not-too-harsh sun, sand, and sea to chase away any impending winter blues. Head on over to the world-famous Santa Monica Pier or shop till you drop at Third Street Promenade. Of course, there’s also the good old beach itself, where you’ll find surfers, beach babes, locals, and tourists alike mingling festively together at Pacific Park amusement park, the outdoor gym at Muscle Beach, or on the historic Looff Hippodrome Carousel-- there’s also Bergamot Station in the heart of the city, which houses several art galleries to check out.
Tamarindo and Smara are two of the most popular beach areas, but there are other good choices in the area as well. This part of Costa Rica is known for large chain resorts on the beach, and the 4-star resorts can be pricey, while the more traditional 3-star hotels are still very reasonable. Costa Rica is obviously one of the hot countries in December in both temperature and popularity, so book early.
You’ve got a pretty good budget so you can afford to go almost anywhere, assuming you are okay with renting one or two houses or villas instead of 4 hotel rooms. If you are willing to fly all the way to Asia, your best bets would be Bali or one of the Thai islands, probably Ko Samui or Phuket. In all of those places you should be able to rent a house or villa near the beach and then do activities and day trips very easily.
Southeast Asia is easier to deal with, and there are cheap flights connecting in the Middle East and landing in Bangkok, Kuala Lumpur, and Singapore. Each of those is a very interesting city, and there are many smaller places to go in the same region. In Malaysia there is Penang and Melaka. In Thailand there is Chiang Mai and quite a few others in that area. In Laos you can visit Luang Prabang, which sounds like it could be a winner for you. And there is also Siem Reap, which is home to the amazing Angkor Wat temple complex.