Too much for one trip?

Hi all,

Husband and I are both planning our next big trip for jan/feb next year. Have a wedding in thailand we are attending so planning on being there about 2 weeks, visiting Bangkok, khao lak and chiang mai. Husband really wants to go to Japan which we could do for maybe a week before or after and was wondering if you think it would be too much for one trip? 3-4 weeks is all we can get off work, flying from NZ