Did your landlord provide you a copy of their ID card and blue house book when you signed the contract? If you have these 2 things then you can register on the TM30 website and file the TM30 yourself.
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You should be asking for copies of these anyway when signing a rental contract to prove that the person renting the property is the legal owner and that they are who they say they are.
I have a Bangkok Bank account opened in 2022 with a tourist visa, Kasikorn and SCB opened over a year ago with a Thai language ED visa. So far no problems with any of these 3 bank accounts. Nobody knows what will happen in the future but for now I think you are ok as long as you opened your accounts with an eligible visa at the time of opening the account and you are not from Russia or Myanmar. Most of the people with frozen Bangkok Bank accounts opened them with a tourist visa or DTV more recently since the policy was changed to disallow it. It seems they are targeting these recently opened accounts along with Russian and Myanmar account holders more broadly.
If you have a non immigrant visa now and are thinking of getting a DTV in the future then I recommend opening multiple bank accounts now to give yourself more options in the future.
Cash in a brokerage account is usually not accepted at most embassies. The 500k has to be in a bank account. Some people have even been rejected for having the money in Wise because it's not a real bank. You will likely need to withdraw 500k to your bank account and apply again at an embassy that doesn't require seasoning of the funds.
It depends which city you are in. You can get a 5 year license with an elite or DTV in Chiang Mai for example. Technically you are only supposed to get it with a non immigrant visa but seems that every DLT can make up their own rules.
It's not a very popular visa right now because it only gives you 60 days per entry, the same time you get with the visa excemption for most countries currently.