For a Non-o based on over 50 there is no need for proof of relationship in the application. You have applied for the wrong category. You only need to show £18k as a final balance on your latest bank statement and a photo of your UK driving licence for proof of location
Anonymous participant 315 as my previous comment to extend your entry in Thailand you MUST have 500k baht equivalent minimum in your bank account anywhere in the world for at least 30 days before the application date of extension