Hi Hitoshi Kumada san,
We do not provide Theta JB and Theta JC thermal resistance values for our flash devices. Instead, we can provide the parameter "Psi JT" (thermal characterization parameter from device junction to package top). Refer our application note available at: https://www.cypress.com/file/210756/download for more details about the usage of Psi JT. Please feel free to ask if you have any other related queries.
Psi JT for S25FS512S (SOIC16) = 7.8°C/W
Thanks and Regards,