The immigration people at Hua Hin are very good. You will have no problem getting an extension there if you follow the fairly simple requirements. They have a spot to pick up the relevant forms and a knowledgeable photocopy lady that prepares the required copies of everything and bundles them up. It usually takes less than an hour in and out after that in the queue. You should have no problem. Your GP will know you don't have the conditions listed for the medical, assuming you have been going to him for some time and will not need to actually test anything. The diseases listed are pretty exotic!!

I don't think so.

Not needed in Hua Hin. YMMV.

If you go late, you could get deported. You'll be in the country illegally. Unlikely but a possibility.

What about getting an O-A for yourself. You are over 50 so should qualify. I believe your wife can be under 50 if she applies with you at your countries embassy. Check your countries Thai embassy Web site. This will give you a 1 year ME. No need to do any border runs. Come and go as you like.

As Tod said in the first reply, you can convert a tourist visa to a non-o in country.

OK now I see your confusion. The income letter is valid for six month from issue until you take it to immigration for your extension. The extension of stay lasts 12 months.

Australia is just a walk in for the income letter. They have stat decs there and a sample preamble. Just take your passport and proof of source.

Is your income coming from an Australian source? You need the letter annually when you redo your extension. You will need the non-o visa first which you don't need to be 50 for. The income letter lasts six months. You shouldn't need an agent if you have all your docs.

The income letter lasts six months.