Hi, I understand that I can put a thai friend as my local guarantor in Thailand on the visa application form.   However, can someone please explain what are there responsibilities in agreeing to this?   I am applying for the O-A long stay visa from Hong Kong and am a UK national aged 57.  I would just like to understand what I am asking them to agree to and why.  Thanks. 

It's a formality, there are no ramifications or responsibilities. Nor will they ever be contacted. It's simply a contact number type of thing. 

Ok, thank you.  

well technically and officially, your thai friend will be responsible from you and your acts. as the word says 'guarantor' your friend confirms that you are ok to get this visa, he knows you and put himself into the line for you. If you do something and disappear they will find him and try to get the info about you from him. thats all

Thank you for clarifying.