Speaking just about the gay bars in Jomtien Complex, I think 100% of them would reopen almost immediately. They've been paying their leases continually for the past 18 months waiting for the green light to reopen, I seriously doubt we'll see too many laggers.
As far as the sum total of bars in Pattaya (all 10,000 of them), I imagine some would reopen right away (similar to the Complex) and others would be reopening on a more gradual/incremental timeline based on tourist-flow and economic forecast.
The Thais are one of the most resilient cultures on earth based on what I've observed. They've been holding their breath and living on peanuts this long, and I don't have a doubt in the world about their abilities to swing back into action when the light turns green.
Once the money starts circulating in the bar scene the working boys will find a way to return. When most of them came here years ago their pockets were empty just like they are now, and they know how to put the pieces together.
At least that's how I see it happening in a REAL REOPENING scenario.