How do I declare my nephew's stay in Thailand and extend his visa exemption?

A user is asking how to declare their nephew's stay in their condo while in Thailand on a visa-exempt basis for 29 days and inquiring about the process to extend his stay. It was suggested that if the user is the condo owner, they need to submit a TM30 form at the local immigration office detailing the nephew's stay. Furthermore, it's mentioned that the last day to apply for an extension would be the 29th day at the local immigration office.