When you apply for a visa outside of Thailand you can use any bank around the world so long as their statements meet the requirements set by that embassy or consulate.
Therefore having the equivalent of 800k in a UK bank would be fine. The statements don’t have to be stamped or signed.
The “first” report since entering the country - each time. Since most on a DTV will only file one report during the 180 day stamp then all of their reports will be their “first”.
Should you time things so you need to do a second report you can do that online.
NZ charge nearly 40,000 baht to apply there. I think Laos does them for 10,000, but it’s probably going to cost you more than 2,500 baht to get there and stay during the processing time.