Do I need to show 500,000 Baht in my bank statements for 6 months or just on the most recent statement for my Thai visa application?

Put the 500.000 Baht in 1 account, much easier for the Embassy to deal with.

Make the application simple, but cover all the requirements of that specific Embassy you apply at. ( Different Embassies, different requirements, so you can’t get exact answers without telling what Embassy )

The deposit is meant as a guarantee that you can pay for yourself if for example you need to go to hospital, and pay before you get treatment, or other big sudden expenses, so no good idea to dig in to deep of the deposit, you may suddenly need it.

Depends

In Israel for example only show the amount , not necessarily for months

On the UK application form it asks for 3 months but if in different accounts you can upload merged, then compressed PDFs using ILovePDF as all documents maximum upload is 3MB.

Depends on the embassy you use. Search using the group search tool

Appears to be different requirements between embassies.