After 1997 crisis Thailand rebounded spectacularly but not without a scratch. Monumrnts of that economic collapse are dotting Bangkok here and there, most prominent I guess, one for all to see is shell of highrise right beside Saphan Taksin station.
About post's main issue my prediction is that as soon as conditions will return to something resembling normalcy and borders will open, Silom/ Patpong will rebound quite fast. Humanity likes good times and this neighborhood is good at delivery of that. But most likely not all bars and massages will re-open and not all our favorite guys will return as in meantim ethay may find other opportunities.
I'm in talks with IMF and fully committed to support their package for Thailand with my own contribution as soon as it will be feasible ie. borders will open , airlines will start flying and I don't die of virus or something in meantime. You have it in writing here