I would love it if that were true. I am emailing the embassy with my balance letter and a print of my account overview (from my online account) now to see if they will accept them.
I do not. The money was transferred from an investment account that does not generate traditional statements. I may have to wait until the end of the week when my official statement arrives. I was was just hoping to apply sooner and that someone had luck using an official balance letter in lieu of not having an official statement.
There are embassies, where when applying separately, the same 500K is used as proof of funds for both parties, in the primary applicant's bank account. That seems to be the norm, actually. Ho Chi Minh, for example, said they needed to see 1 million (and allowed you to apply at the same time), but Vientiane, Taipei, and Jakarta only need 500K (but require that you apply at separate times). So there is some variation, and I may have answered my own question with the established pattern noted above, but I just wanted to be sure with Phnom Penh.