South east Asia

I am looking for some recommendations for south east Asia. Main concerns are itenary and weather.

Currently planning to do south east Asia in July for about 4 weeks. Currently I am thinking of hitting Thailand, Laos, Cambodia , and Vietnam. I have an interest in experiencing the culture, nature, and diving.

Q1: how bad will the weather be? I understand it will be monsoon season but can anyone give some context for how bad this will be? Is it still fairly manageable or will it be miserable with many wasted days and not being able to fully enjoy the nature (ex: mud + overcast)

Q2: itinerary .
I am looking for all sorts of suggestions for itinerary and places to hit. Currently I am thinking the banana pancake route and I am wondering if it is possible to do this in 4 weeks. I am also looking for any recommendations that you may have here. I also want to add that I am ok with a slightly rushed trip, I don’t get much time to travel and I am looking to optimize what I can see/experience.

Thanks of all your help in advance!