My experience in May using a travel agent in Siem Reap was odd but worked. They wanted a photo and usual copies of the passport. They copied six months of my bank account statements in the USA. Charged me fifty dollars or so and took it off to Phnom Penh. A week later I had the SETV. No onward travel ticket required.
just to clarify....I will present a financial document upon applying for the Non O and when applying for the extension three months hence provide a new (second) financial document. Correct?