When I went to Ho Chi Minh ( Saigon), I was surprised how crowded it was, full of motorbikes, and the humid weather, I could visit the mausoleom of Ho Chi Minh, the History Museum and the Pagoda of the Emperor of Jade.
To go from Phnom Penh (the capital of Cambodia) to Phnom Santuk, I had to take a bus, even the distance was not that long (about 200 kms) it took around 4 hours to get there, I had the occasion to see the typical houses in Cambodia during the way. Once you get to Phom Santuk you have to climb up 800 steps if you want to see the temple. It is worth it to see.
When I decided to travel to Vietnam, one my favourite destinations was Hoi An, this city it is a mix of influence between Chinese and Japanese, and it is beautiful it has an old Japanese bridge or you can see the streets decorated with handcrafted lights. You can also see the Hoi An Pagoda.