Just to clarify, you don’t “add them”, but submit separate applications (including the fee) based on rational that you, father, has a DTV. So once you have your DTV, you can submit applications for each family member
well if you can’t apply, because you can’t visit Phnom Penh for 30 days, then you can’t be as successful. Right? You can’t apply and therefore, you can’t be approved. Furthermore, we have no data one way or the other to show approval by nationality for those who are able to successfully apply. So we can’t say one way or the other.
the problem is, for some people with certain passports, which require 4+ weeks to process, it is impossible. Someone from a Europe or the US can fly from Thailand to Vietnam on a 30 day tourist visa and apply and then get a DTV visa in 5-10 days. If you are from other countries, it takes 4+ weeks, but can you stay in Vietnam on a tourist visa for 4+ weeks? Can you stay in Indonesia for 4+ weeks? If not, you are forced to fly back to your home country and apply (which is more pricey) while others can just hop over to a nearby county and be back quickly/cheap. One can argue that it is set up this way to make it very difficult for certain passports holders.