I agree, I did my initial licence at a different office to my
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year extension and the process was much the same and very easy.
It took about 30 minutes for the first one and an hour for the extension after 2 years.
I didn't go to check my paperwork was in order, so it was one visit each time (I just keep a file with everything they could possibly ask for, just in case).
Very simple, no need for agents and no need to risk not being insured by avoiding it, and using the IDP for more than 90 days.
Pattaya and Jomtien are very similar as they are next to each other and the main attraction is the bar girl scene with a lot of sex tourists. I wouldn't swim in the sea there either.
Hua Hin is a nicer place IMO with cleaner beaches, but the population is mainly retired expats.
Phuket has a bit of everything including a lovely old town and nice beaches.
Krabi is lovely, but I think it would get boring quickly if you lived there and the main resort area gets very busy in high season.
Koh Samui has a young vibe and nice beaches, so it could be a good choice for you.
Places like Samui, Krabi and Phuket are much more expensive than Pattaya/Jomtien/Hua Hin, if that is a consideration.
As others have stated, travel around and see where you like.