I can't speak to phuket. As far as chiang mai goes we were underwhelmed for the city experience there. If it were my "honeymoon" and not just a big trip taken with longtime partner after wedding I would definitely look at resort experience nearby with a day trip to chiang mai. Luang prabang on the other hand we loved, it had the vibe/experience we thought we would get in chaing mai reading about it (obviously entering another country has its own hassles these days)