Can't do much until you're 50. But once you reach that point, it's just a matter of paying an agent if you don't want to deal with it yourself. Around $2k to get started. Subsequent years significantly cheaper (~$400-500)
3 months for what? 3 months until you will travel? 3 months that you'll be in Thailand? 3 months for your class?
How about providing some BASIC information with your question?
Who are you? What passport do you have? What DTV did you apply for? Where did you apply for it? What do you mean by "our" DTV because a visa is for a specific person.
Agents aren't going anywhere. The agents in Pattaya just put their customers on a bus to go to different branches of Bangkok Bank, or switched to different banks. The heat was just on in Pattaya. How many crackdowns have you read about in Thailand over the years? This will blow over and things will return to status quo.
This person is talking about a letter to use for 12 monthly transfers. Multiple Bangkok Bank branches have refused to issue this anymore, and without it they cannot get their extension.
Though it's ultimately lazy immigration officers that require this. They do not want to go through the bank statement and find the 12 transfers, so they want the bank to put them all in a letter. Bangkok Bank has said they will no longer do this at some branches.
Your documents have to be authenticated by the Thai embassy in your home country and then verified by the MFA in Thailand. You'll have to get an agent to do it for you if you don't want to go back to do it yourself.
You need to bite the bullet and go to your immigration office and ask them for their handout listing the requirements. That's because each immigration office sets their own requirements, and they change from time to time. The best practice is getting their updated list every year before you will go and apply.