Thanks all for your help & responses. It is clear now I need to do TM47 (90 day report form) & TM30 (Landlord or Hotel stay form). It is simple & straightforward. However, if I stay in Bangkok having an apartment contract with a landlord & I am travelling to a place within Thailand (e.g. Koh Samui), can I go to immigration office in Koh Samui or any nearby office with my Bangkok TM30 form? Or I need to come back to Bangkok to do 90 days reporting?