What are the financial proof requirements for a METV application at the London embassy?

Hi,

When applying for METV from london embassy,

1. For the financial proof, does the 3 months of bank statements all have to show over 20,000 baht for each month or is it just the most recent balance.

2. can i use an cash ISA as proof of funds

3. If my plan is to fly to BKK from uk , return to the uk, and then fly back to BKK over a month later , Should I show all of these flights on the application.

Thanks