I tried, but couldn't quite understand the reply (my Thai isn't quite good), I only got that they said to come back to do it in person next time. BTW, it's a remote immigration office - rural part of Kanchanaburi.
Getting a lease agreement is not really the issue, just a matter of looking for a place to rent - something that would need to be done anyway since the plan is to stay long term for retirement. The issue is the 3 months of receipts... Not possible, cos if u came in on a TR, even with 1 extension, that only makes up 2 months, and u gotta apply before it expires.