what office are you using? This is the official line. What ever happens outside of those distinctions anyone who lives in Thailand already knows about. If your entering the country by air Bangkok rules generally apply.
Use a currency exchange/trading service like Wise. Transfer fees are very reasonable, and there's no risk of loss or robbery. Also no limits on aggregate transaction.
I have been using the TR60 since 2008. I show the flight in, and after 6 months the outbound flight. That's it. I have done many air and land 60 day exits arranging transport from within Thailand.
The overnight train to Nong Khai is inexpensive and a generally good experience. The bus service at Friendship Bridge is great, ฿20. There's a bus to Vientiane on the other side should you decide to stay awhile. Entry on arrival is now $40. evisas are available online.
In regards to application location your home country or Thailand. Financials and other docs are accepted as submitted from within your home country. Here you will be jumping through more hoops. @home you will have access to the physical documents, and generating any needed will be vastly eaiser. As to casual work depends on the particular location. I once had the headmaster at a school invite me to teach English at his school a couple days a month. The COVID-19 emergency decree shutdown the school before we arranged things.
vague misinformation? It's definitely a click bait to a financial advisor, but has some good information directly attributed to the revenue department.