I have searched but not sure if the information I have is the latest and greatest.   

My wife and I are going to Thailand soon and will be applying for a Retirement Extension, both are over 50.  Does she also have to show her own 800k deposit and/or monthly income or can she piggyback off mine through a dependent type "visa".

You wife does not need to meet any financial proof to apply for her extension based upon yours for being your spouse.

What type of visas will you be entering on?

 I suspect it will be visa exempt or on tourist visas which will require you to change to a non immigrant visa (category O) by applying at a immigration office. Your wife will not be able to do the change at immigration. She will have to go to a nearby embassy or consulate to apply for a single entry non-o visa.

Either if you can get a 1 year extension of stay with 800K in the bank in the applicants name.

 

Once that extension is issued the other can apply, as a spouse, for an extension without any additional money in the bank. Effectively the second applicant piggybacks the extension of the first.