Probably better to understand that every entry gives you 180 days in Thailand. Each entry can be extended once for 180 days. Maximum time in country per entry is 360 days after which you must leave. Re-entry gives another 180 days again extendable.
the fact that your money is taxed in the UK is irrelevant to Thai tax law. The DTA gives you a tax credit for UK tax paid but depending on your Thai personal allowances and deductions and remitted amounts you may still have a Thai tax liability.
Bangkok Bank Jomtien. Passport, copy long term visa stamp, copy 2nd government issued photo id, copy 1 year lease, certificate of residency. At least 30 days remaining on current stamp. Different banks and even different branches may have different requirements.
that depends on your personal situation. Were you tax resident in the year when the funds were remitted? If so what was the source of the funds as that determines if the funds are classed as assessable income or not.
firstly you must jump the hurdle of being tax resident. Then you need to clarify what “no income” means. If you are tax resident and remit no assessable income during the tax year then you don’t need to file and don’t even need a TIN.