If you stay over 180 days in a calendar year then yes you become a tax resident based.
However, if you have a DTA then that can override that. Especially on a tourist visa, you will likely be a tax resident of your home country as well. So will need to read your DTA and work out which country you are deemed a tax resident of.
there is no written limit on flying in visa exempt, but immigration officers can and eventually will deny entry to those who abuse the system. Sometimes it's after 4-6months, whilst some make it years before encountering issues.
they use to have these coin counting machines at banks, they got rid of them. So clearly it wasn't worthwhile for the banks. There might still be one left at SCBX Park.
How long do you want to stay in Thailand? If you're a tourist then the best or easiest option to stay a while is probably the METV which is a multiple entry tourist visa where you get stamped in for 60 days each time you enter, this is valid for 6months. You can stay almost 9 months with this visa if timed perfectly, add a few land border runs at the end and you could stay a year.
Otherwise there's the expensive options others have posted.
that's good, so all he'll have to do is talk to military department at District office, they'll make him pay a small fine (couple hundred baht), then discharge him to the inactive reserve unit as he's over 30.