E-visa allows tourists to do administrative procedure by themself like in Vietnam. E-visa fee has been regulate by Ministry of Finance for 30USD+ 6US for processing changes. and now, you pay directly onto their website. It takes around 3 business days to aplly.
Currently, some countries get visa exemption : Laos, Malaysia, Philippines, Singapore, Vietnam, Thailand, Indonesia, Brunei Darussalam, Myanmar.
Countries all around the world can get a visa approval.
Here, the link for the official website : https://www.evisa.gov.kh/