You didn't provide the only information that matters, which is your passport country. That determines what you can qualify for.
There is no such thing as a 60 day tourist visa on arrival. There is a tourist visa that you have to apply for before you travel from a Thai embassy. There is a visa on arrival that is applied for and paid for at the airport and only available to certain countries and is only for 15 days. There is visa exempt which is probably what you are asking about and it's not any visa at all. But it's only available if you are from certain countries, and you didn't provide that information.
There is no ETA. There is Visa on Arrival. This is for a specific list of countries that can APPLY for and PAY for a 15 day visa at the airport.
There is visa exempt, which is for a much larger list of countries. These people don't get any visa, they get a visa exempt entry stamp for 60 days.
There is visa waiver, which is a bilateral agreement between countries. This is anywhere from 15-90 days depending on what country your passport is, and is also not a visa.
YOU don't get to choose. You qualify for one of them.
If you don't meet the financial requirements of your visa, you cannot get next year's visa by yourself. You will need an agent. You have to plan 1-year ahead if you want to break out of the agent cycle, because your 12 month bank statement that you submit for your extension must be able to show you had the 800,000 last year and never dropped below 400,000 the rest of the year.
And that's the easy ones. There are agents that take your passport to a province hundreds of km away that's known to be a province that agents use, and get your stamp from there. If you get one of those, then you simply cannot do it yourself, period. Immigration will not touch a passport that has one of these extensions, and you will 100% be stuck using an agent.
"Worth it" is subjective to each person. Some might think it is worth it to not have the money in the bank, but you are then stuck using an agent every year and paying whatever they demand because you have no other option.
Others think it's worth it to keep their own money in their own bank account, where they can withdraw it any time as it still belongs to them, but they must leave it there for as long as they want to qualify for their visa. Annual visa extension price using your own funds is going to be 1900 baht paid directly to immigration.
I'm not sure I understand your question. What are you asking about? If you're asking about visa on arrival, the difference is you either qualify for one or the other based on your passport. You don't get to decide which one you want.
it's the same thing. But each residence certificate is issued for a specific reason so you can't use the exact same document for both of those things. You must get a new one each time.
If you really must leave, and it will be saving enough money, then you can look at using a service like this
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It's an agent "VIP Entry" service. Not the same as normal fast track that just gives you access to a shorter line. This service is where you tell the agent your circumstances and then they will get in touch with their contacts at the airport and give you a price to guarantee that you can get into the country. I think it starts around 3-5,000 baht depending on your circumstances.
They will meet you as you exit the plane, and then walk you to immigration and tell you which line to get in so you don't experience any issues.