Can I use a visa exemption for the Phuket Sandbox and extend my stay in Bangkok before November 26th?

The ability to extend your stay after arriving in Thailand under the visa exemption through the Phuket Sandbox will depend on the discretion of the immigration officer you encounter. Generally, you may receive a 30-day extension first. An alternative suggestion is to enter Thailand with a TR visa, which allows a 60-day stay followed by a 30-day extension.