Anyone can correct my understanding.
If I want to get a retirement visa in Thailand, I use visa exemption to enter Thailand and apply for 30 days extension to sufficient time to get NON-O (retriement) visa with required documents and proving the Thai bank account had THB800K. When they are approved, the NON-O visa allows staying for 45 days. After that, I go to apply for a one-year extension before expired. That finish, then repeat the process to get a 1-year extension next year.
Am I right? I want to enter Phuket / Chiang Mai sandbox and do it in Chiang Rai immigration through this process to get my visa.