Did you look at tours on AB-ROAD?

http://www.ab-road.net/tour/list/OSA...esearch_flg-4/

For flights + beach resort hotels, the best deals seem to be in Thailand (e.g. Pukhet) and Indonesia (e.g. Bali). One example here:
http://www.ab-road.net/tour/detail/O.../toursuffix-1/

Taiwan flights tend to be rather expensive despite the relatively short distance (although the business traffic should be slack around Xmas/New Year)

... Korea is not warm in December.