11 hours ago, timendres said:

You are correct that the original visa has expired and no longer exists. However, extensions are "based" on something. An extension can be based on a work permit, or retirement. When I needed to change from an extension based on work permit to extension based on retirement, I was told that I could not make that change with the Non-B visa that I originally used to obtain the work permit. I was told explicitly by CW that I needed to exit the country, re-enter, obtain a Non-O, then file for the extension based on retirement.

1 year extensions are based on having Non Immigrant status, and the 'reason' can vary.

Orders only state must have Non Imm but don't define any particular category.

I've know those on initial Non B visas to later apply for extensions for reason of retirement or Thai family, whilst others like yourself have been told to obtain the Non O first.
Another example of Immigrations inconsistent use of discretion.

Just now, Liquorice said:

1 year extensions are based on having Non Immigrant status, and the 'reason' can vary.

Orders only state must have Non Imm but don't define any particular category.

I've know those on initial Non B visas to later apply for extensions for reason of retirement or Thai family, whilst others like yourself have been told to obtain the Non O first.
Another example of Immigrations inconsistent use of discretion.

Yes. Others in the forum have stated that they successfully changed from Non-B to Non-O in-country.