In the middle of April I am planning a short one week honeymoon with my Thai wife but would like some thoughts from the forum as to which local country from Bangkok they would recommend. We both like visiting places of architectural interest, places of historic interest, places of natural beauty, and of course the malls or street markets.

Wow. Quite a few options! I'd probably recommend Vietnam. You could spend a month there and not be bored. Hanoi and surrounds would be great. Halong Bay. Sapa. And Hanoi itself. Old town is great to explore. And crazy! LOL

Another vote for Vietnam where you are less likely to be breathing the heavy smoke pollution that may still be permeating the air in the other countries in mid-April.

Go holiday has some wonderful trips to Myanmar even though not on the list. If you only have a week may want a tour as can have a lot of non productive time finding things by yourself.

Can spend 3 or 4 days at Siam Reap then come back through Phnom Penh. That's a nice trip.