Can I change a tourist visa (TR) to a non-B visa within Thailand?

Yes, it is possible to change from a Tourist Visa (TR) to a Non-B visa inside Thailand, but there are specific requirements. Your employer may need to contact the local immigration office for guidance, as not all offices allow this conversion. Moreover, there must be at least 15 days remaining on your current stay for the process to proceed. It's recommended to have your employer handle the necessary paperwork and visit the immigration office together to ensure compliance with all requirements.