I may be guilty of overthinking this but I recall when originally applying for a retirement visa (before I married and switched visas) that I had to supply many notarised documents including a medical certificate and police check. Would that still be the case in the circumstances we are talking about here?
So, to wrap things up.. it seems the only fail safe way to ensure a smooth transition from marriage to retirement visa (ignoring the income option) if time proves to be of the essence is to try and ensure 800,000 baht in the account even if you are on a marriage visa with a 400,000 baht requirement.
Worst case scenario is if the wife dies just before said deadline unless there is a special dispensation (which nobody has mentioned so I must assume there isn't one).
There are two issues here. Increasing the foreigner's funds from 400,000 to 800,000 baht. This could take a bit of time which is why I asked about a period of grace, by which I meant dispensation beyond the deadline for extension of visa.
So I ignore the computer generated request, turn up in person for the new 90 day report then assume it will subsequently be in the system so I can do all future applications on line like before? (The online process is very good IMO.)