E-Class Visa, EB (Business) Extension
Under 55 the retirement extension is closed, so what you can use depends on whether you work in Cambodia. The EB is the long-term option, and it needs a stamped letter from a Cambodian employer, a registered business of your own, or an EB holder to be the dependent of. An agent can file it for you, but the letter has to come from work you really do: a letter from a company you don't work for does not meet the requirement. It gives no right to work by itself: any work in Cambodia needs a permit from the Ministry of Labour, and the immigration office can ask to see it before renewing a 6- or 12-month extension. Cambodia has no digital-nomad visa, and the government has not said whether remote work for clients abroad needs a permit, so ask a lawyer before you move. At 55 or over take the retirement extension instead, even if you work part time, because it does not depend on an employer's letter.