Prices go up a bit when you go south into Malaysia, but it’s worth it if you’ve got the money. You might even consider Myanmar as well, which I’ve yet to visit, but I keep hearing great things about. It’s honestly the perfect time of year there. By April it’s insanely hot (the hottest month of the year), but December through February is lovely. It’s all quite safe as well, as long as you keep your wits about you. I’m happy to help with more information if you need it.
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.