@Isan FarangJust a couple of tips that you may or not be aware of:
1. Make sure that the document you provide with proof of address shows exactly the same address as your home address in Thailand.
2. If you are using a Thai debit/ credit card to pay, make sure that it is authorised by the bank for overseas payments. Payments are debited in UK.
My neighbour had his payment declined by the bank and was informed by VFS. Fortunately he visited VFS to resubmit payment, after speaking with the bank to authorise payment, and all was well in the end.