That seems high as an initial payment.

What is the plan for year two, another year up front or on a month to month basis? If it's on a month to month basis this would leave the landlord without any security deposit which most would not permit and it sounds unlikely your landlord would be happy with that arrangement given their demand for a full year in advance. You should make sure there is a clear understanding on this point to avoid a nasty surprise later.

I suppose it all depends on how much money we are talking about; you might consider it is worth a punt.

I heard that you can register the lease at the Sangkat with you and the landlord both present to thumbprint the lease. This might give some protection should the landlord sell the property and keep quite about your status as a paid-in-full tenant. To be clear, this is what I have heard, I do not know for sure so you might want to post another specific request for information on this aspect.

Good luck

One month per calendar year is not unreasonable. But I've always negotiated a few months off longer leases here.

A year up front = alarm bells.

I'd never pay 1 year up front for anything>( except car insurance which you can not pay monthly)
to much can happen