Korean Air doesn't begin boarding until exactly 30 minutes before departure AND they always line up huge long line, so you'll be ok.

If you are delayed - there WILL be someone waiting outside the plane door to greet you for a personal escort (sign with name or even just "Rangon passengers" for instance. Even those in Y get this service :-).

If for some reason there isn't anyone - you can absolutely show your next boarding pass or itinerary to the first staff you see and you can cut the line zero problems no questions asked. They're really good about this.

AND T2 is just not that busy these days as it only serves basically Korean Air and three other airlines with 1-2 per day.