Exit Visas must be applied for in person at the DoI Visa Office, they are only valid for 7 days, so you need to apply within 7 days of your intended departure date.

Exit Visas are only required if;
- Departing on a new passport without a valid Visa/EOS ie. You have a new passport because the one with your visa/EOS was lost/stolen/damaged, foreign child born in Cambodia
- passport holder has overstayed by 30+ days

Supporting documentation requirements vary based on the circumstances...detail why you need Exit Visas and I'll advise what you need (your previous post wasn't clear on why you need Exit Visas). Does your daughter not have a Cambodian passport?

OK so she has a new passport...head out there and see if you can get a K-type Visa issued, some people have still been having luck getting K-type Visas issued in-country, but others are being told no, need Exit Visa and get the K-type VOA upon return. All depends on the officer on duty at the time.

If you need to apply for the Exit Visa, You would think that her old passport with K-type Visa would be sufficient, however, once again that will depend on the officer on duty on the day, so take all necessary supporting documentation such as birth cert, family book or Carnet de Residence, parents passports, etc. and don't forget 1x Passport pic. Exit Visa is $30.

Alternatively, get her a Cambodian passport and avoid all the hassle of Exit Visas, K-type Visas, and she'll even get her airport tax refunded.