You must meet certain requirements to enter Cambodia, even if you do not require a visa:
All fees are non-refundable and will not be refunded if your visa application is not successful.
All the visa types of Cambodia are extendable. Tourist visas can be extended only for another 30 days at the Immigration Department. Ordinary visas can be extended for up to one year.
Despite it rarely happens, it is possible to get refusal from Cambodia e-visa application.
Yes, you can also apply for Cambodia visas at the Cambodian embassies/consulates or visa application centers.