If you're rich enough to retire under 50, Elite visa is the answer.

How much you will need to retire depends much more on your lifestyle and future medical issues than anything specific to Thailand, especially for younger retirees as costs of living tend to converge across locations over time.

Many people have got caught out by deciding to retire in Thailand based on overly simplistic calculations, and then end up having to move to even poorer countries as living costs rise or return home due to uninsured healthcare needs.

Employer will sort it

Maybe get an education visa to study English.

Yes, I've walked through with a random Thai I met on the plane before

I believe the same visa rules apply regardless of which team you bat for.

Is this a trick question? Why wouldn't you just bring the dog in a car?

What's your nationality and age? Do you mean 1 visit to Thailand for 6 months or many short trips totalling 6 months? How do you fund yourself when you're in Thailand?

Bangkok starts becoming very trampy within a few miles from downtown, but the key point if you're not bound by work commitments is that you can time your journeys to avoid the worst of the traffic - just choose somewhere with easy access into / out of the expressway system, which is an amazingly fast way to get around the city, except during rush hours.

It depends on your professional skills / experience. If you don't have any that are particularly unique / valuable, you will essentially be limited to teaching English, which doesn't pày enough to make sense for anyone except young backpackers who do it for the "experience". Working remotely in Thailand for a company in your home country may be a good option if you have some skills, but nothing unique / valuable enough to standout in the job market here.