I am in Thailand on a retirement visa (2nd year), and my 16 year old daughter has chosen to live with us. She's been admitted to an international school (High School) and is currently here on a one month tourist visa. Is there any way to change status to an educaqtional visa (no problem getting school letter) at immigration here, or do we have to go out of Thailand to a consulate?

Although there is a procedure to do so it will require several layers of paperwork from her school so if they are not advising you on this they should be. As daughter does not appear to have a tourist visa (normal 60 day entry for most nationalities) it would require application during the first week of stay (21 days or more remaining) to obtain a change to non immigrant visa at an immigration office.