Can I transfer from a 30-day visa exempt to a retirement visa without leaving Thailand?

Yes, it is possible If your current stamp is still remaining days, but a number of days are local immigration offices specific. Most offices require you to have 15 days or more for application but in Chiang Mai and some others 21 days (15 working days).

Go to your office to get the latest requirements for an initial in-country Non-O visa based on being over 50.

They speak English at most offices, you can call by yourself.

Here is a rough timeline to get an in-country visa then 1-year extension.