How can I transfer a non-B extension of stay to my own company without leaving Thailand?

To transfer a non-B extension of stay from one company to your own, you must first obtain a document from your current employer confirming the end of your employment. Then, visit the immigration office that issued your current extension to cancel it using this paperwork. After cancellation, go to the immigration office relevant to your new employer with all required documentation to apply for a new extension for the change in employment. Additionally, don't forget to coordinate with the labor office to update your work permit, as it is essential for the extension process.