My bad. You’re right. You can’t not do non-o while in Thailand because the purpose of the visa is to enter the country.
You can, however, get an in-country extension of stay. E.g. based on marriage or based on retirement; they are for one year. Or shorter extensions for other reasons. (I don’t know them all by heart)
Here’s the explanation of the Thai e-visa system for Netherlands:
IMPORTANT:
Thai Visa is for entering Thailand. It is therefore issued to those who are outside of Thailand and will visit Thailand. Therefore, your visa application will be rejected if you are already in Thailand during the visa process.
Royal Thai Embassy, The Hague, has the authority to provide visa service only to those who are in the Netherlands for the entire visa process. Therefore, your visa application will be rejected if you are outside of the Netherlands.