I found the same thing in Thailand with a Nestlé diet drink that they claimed aided weight loss. Although it was low fat it contained an enormous amount of sugar. I wondered at the time if the statement on the packet would have been legal in the US
Bangkok and Chiang Mai immigration offices make decisions about marriage extensions for regional offices. Retirement extensions decisions are made locally
You do not need a Thai bank account if you apply for a non O visa, based on visiting your Thai wife, outside of Thailand. When you have a non O visa you can open a Thai bank account. The 400k baht must be in your Thai bank for 2 months before you can apply for a 12 month extension based on marriage. As your non O visa lasts for 90 days there is time for this but don't hang about. Ifyou apply for a non O visa while in Thailand then you do need a bank account. This is where your confusion is. HSBC account cannot be used as it is a foreign account. HSBC only operate commercially in Thailand. There is no retail banking.