I don't know where you book. But neither KLM, AF nor Lufthansa, Austrian, Swiss nor Finnair from BKK to HAM include checked baggage in the price shown on Google.com/flights, their respective websites, momondo or sky scanner. Each of those offer you to add checked baggage in a second step while booking at additional cost as of 2 days ago. Extra fee for one checked bag was KLM, AF 3000 Baht for the round, FinnAir 70EUR one way, LH Group between 4700 and 5600 Baht for the round.