LENGTH OF STAY for American Citizen

Are 60-day or 90-day Single-Entry Visa available for Americans through the services of CVASC?
I am currently in Phnom Penh trying to compile information on the China Visa to complete an Itinerary. I consulted an agent who called the PRC Consulate in Phnom Penh and the response here was: 1-year, Multiple-Entry (1 month stay limit) was the only option available for USA and Canadian citizens... and for something on the order of $345. He suspected it would be the same in Bangkok. Could not get to anyone over the phone or email. Does anyone have experience with this and can clarify???