I used Allianz Travel Insurance. Good everywhere, and for many other travel needs, one year policy, and lots cheaper. Just needed a letter from Allianz, stating it covered COVID for $20,000. One phone call and it was provided very easily.
As to opening Bangkok Bank Account, I opened mine, while on Tourist Visa Exempt Stay, in Pattaya on 2d Road. Only needed a Thai National to "vouch" for me, and a residency letter from Jomtien Immigration. Always great service.
Depends on location, bank and branch. I opened one in 2021 in Pattaya, Bangkok Bank on 2d Road. Needed a Thai to vouch for me, and a Letter of Residency from Thai Immigration in Jomtien. Just used my hotel address as residence. Was on Tourist Visa.