Flight 269 should have never left Bangkok
Would have to see the dispatch release for that. And the ops manual, with TAF and trended METARS. And all the updates from the dispatcher exercising his "operational control and flight following" duties.
Tropical weather is notoriously spotty and short-lived. Of course, if the AoT equipment is OTS and not NOTAM'd, and the AeroThai WX is not caveated, then the picture at departure might have been, if not rosy, then not unflyable. Airplanes operate in heavy weather all the time.
But for Pete, I've seen wx get included as a contributing factor, but don't recall it listed as the cause of any accident (not to say it hasn't, just that I can't recall). That's the call that the guys up front are supposed to make, whether a neophyte electing to "continue VFR flight into IMC" or an experienced big iron crew electing to continue an approach into more drastic wx. The SOP's, work limits, and training, combined with experience, are the things that are supposed to aid that decision making and prevent tragedies like this.