If you test positive for COVID-19 and have mild symptoms or are asymptomatic, Thai authorities recommend that you self-isolate at home or in a community setting dedicated to this such as a school or temple, where you can receive appropriate care. This also applies to school age children.
National Health Security Office (NHSO) provides medical support and services for home isolation. To register, you can call the 1330 hotline.
If you have more severe symptoms Thai public health regulations require that you quarantine at either a hospital, hospitel (a repurposed hotel with medical capabilities) or field hospital.
You should ensure that you understand your health care provider’s policies before you take a test as these will include where you quarantine and receive medical care if you test positive.
https://www.gov.uk/foreign-travel-advice/thailand/coronavirus