Bangkok Airways FlyerBonus reward scheme grants an extra 10kg of luggage on all flights just for signing up.
That takes you to a minimum of 30kg even on the cheapest economy airfare and I've never encountered them being particular fussy with carryon weight. I fly with them maybe once or twice a year but have joined their points programme simply to gain the extra baggage allowance.
As others have said lounge access is granted to all passengers both international and domestic.