If you have an actual legal business, that you pay taxes on then maybe, but without a legitimate business then no, as eBay will not give you any documentation stating you are allowed to work remotely, or that you work for them. You need a separate legal business.
that agency has an immigration agent they work with strictly for exempt tourist entries. That's why they told you that. All you need to do is cross the border yourself and return. You're stamped in for 180 days no problems at all.
You better guess again. The question concerns making video content as a job, making money. Which technically they must have a license to be legal. It doesn't matter how many are doing it illegally.
Immigration gets very suspicious if you are using a new Thai bank. You have much more success using your regular bank account in your home country all your business goes through, and that you've had for a length of time.
also get one so you can get a Thai driver's license. After 90 days in Thailand you must have a Thai driver's license to be legal. If you are not fully legal no insurance will cover you if something happens. On the application check both boxes. You'll need three, one to purchase, and then one for motorcycle license, and one for car license. They are two separate licenses.