I was wondering if anyone knew the minimum requirements for getting a Certification of Residence from immigration in Bangkok? Would they do it with a TM 30 from an Airbnb or a TM 47 from a hotel, and what would be the minimum stay allowed by the immigration officer to obtain this?
The goal is to use the COR to open a bank account. I know this is atypical as most would already have a lease , but the reason I am asking is that I am entering the country on a non-immigrant OA for retirement, but because I have a sick parent, I will only be in Thailand for the first three months straight before needing to go back-and-forth to deal with her healthcare. In a perfect world, I would choose to not commit to a one year lease initially and was hoping that getting a COR from immigration would allow me some latitude to open a bank account?
Has anyone done the COR with minimal requirements? Thanks in advance. I’m trying to avoid using an agent if possible. 
TLDR : Answer Summary
To obtain a Certificate of Residence (COR) in Bangkok, you need a TM30 from your place of accommodation (like an Airbnb or hotel). A lease agreement is not mandatory, although it may help. The COR process takes about 1-2 weeks as it’s mailed to your address. Most banks will accept the COR along with your Non-Immigrant OA visa for opening an account. Requirements can vary by bank, and some may still request a lease. It's advised to clarify your situation with immigration, especially if you're not planning to sign a long-term lease.
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