paid 2600 last year, unsure if price gone up, they take you over and way back they buy you lunch. Start like 5am and home before 5pm and we went to ban laem border I believe
And your question about the border: This company take you there, then it's a line where they collect your passport then it's a waiting area where you get your passport back with visa to Cambodia, you cross the bridge, get stamped out, stamped in, cross back and get stamped out to get stamped into Thailand again
Apply non o (retirement), you get 90 days that you can apply 1 year extension on. That you can then apply re-entry permit if you need to go in and out of the country
well now you have 'border run' with car. the company should take you back and forth without issue. If you staying like say Pattaya they take you 5am and you back before 5pm for less then 3k bath. Unsure about Bangkok but quick search in the group you get your answer. If you staying somewhere else, probably another group that you can ask about border run