has explained. If you have longer term goals, say up to five years, the Elite Visa may be a better option. Expensive upfront, but over five years works out at about $10 a day
If you plan to enter and simply leave after nine months there's no point in doing the 90 day report as you'll never have any reason to visit immigration and the officers at the airport don't give a stuff about 90-day reports
I used the border at Chong Mek. Although we live in Bangkok my lady comes from out that way, so we'd combine a visit to her family with a drive to the border. She'd come over with me, and we'd generally spend an hour or two. It's a crap place on the Laos side, but a few shops and restaurants to look at, have lunch and come back over. It's a strange place, with a tunnel that doesn't actually go under anything except a car park. Fortunately there's signs in English pointing to Laos and Thailand!
By law it's required, but it'll never be picked up. Pre-covid I lived for nine years in Thailand on OA visa, using the border bounce to get the free year, and returning to my home country for a visit every two years, picking up a new OA in the process. In those nine years I never had to transfer money into a Thai bank account and never went to an immigration office. Covid killed that but now it looks like it's back on track! I was never once queried about 90-day report, and if absolute worse comes to worse it's a 2000 baht fine. Some people pay more than that to agents to do it for them!