1

I'd do Mekong on a tour. It solves a lot of transport logistics.

If you go on a cheap tour you will still see the things they say you will see but you will be a commodity who is passed from bus to another bus to boat.... but the tours are really cheap so you can forgive a lot.

Phnom Penh is pleasant but if you are on a limited time, you could skip it.

2

We did the reverse tour from Angkor down the Mekong into Saigon, but not with an organized tour. I think that was one of the best choices we made on that trip.

We felt Saigon is worth the visit. From there you got lots of transport option into the Vietnamese Mekong delta. We arrived in Vietnam in Chao Doc with a boat that started in Phnom Phen. On the border to Cambodia the boat will stop and you will make a passport and visa check there, then it continues.

I'd recommend you to priorize time on Siem Reap and Angkor. When we arrived in Phnom Phen, we inmediatley decided to continue down the Mekong and priorize the delta.

3

I took the package tour from Saigon to PP and I hate package tours, and it really wasn't that bad. Cheap, easy, we saw some cool stuff, ate good food.

PP is a perfectly pleasant town, but I wouldn't give up a day in SR or HCMC to be there.

If you do stay in PP, visit Tuol Sleng and Chiang Ek. You'll be depressed for about a week afterwards, but do it anyway.

4

when you come to SaiGon, some more wonderful places you can explore are Da lat, Nha Trang, Hue, Da Nang.

5

How long did you take from PP to HCMC? Which route did you follow?
thank you very much for your kind help

6

It's been a long time but we did the tour on the Mekong Delta to Phnom Penh, Taxi to Battambang and then took a boat to Siem Reap. Sure I loved Angkor (if you've got the time for the three day ticket, leave the big temples to last and work your way from the remote overgrown ones), but it was that boat ride to Siem Reap which really made an impact. Stopping at floating villages, floating through tree tops (wet season I'd guess cos the water was high). I recommend it.

7

What you could do is this:
from HCMC take either an organized tour into the vietnamese Mekong delta (almost any operator in HCMC offers those) or go there on your own by local transport. I did not tour any of those delta villages ecxept Chau Doc, but I am sure there are plenty of people here who have and can give you more details on what's interesting or not.

Then within this delta area, you finish in Chau Doc, take a boat from there upriver into Cambodia to PP.
In PP you may check your options to SR/Angkor with operators. You can go there also by boat, which appears to be really nice, but if I remember correctly it also depends on the time of the year and thus the water level of certain areas.
SR is really nice to hang out. If you find a spot in Angkor that you particularly like but with too much crowd, it helps to go there at sunset. Tourists tend to move to spots then, where they can see the sunset, leaving even places like Ta Prohm with relatively few people and thus quite a magic atmosphere.

8

take hiking in dalat, to Hue you can make a biking instead of classic tour on car, your time is more amazing