It’s best to be safe and comply with the rules. Keep in mind flying from the US is a very long and tedious trip. Who needs any hassles, when one is dead tired. Especially if the plane is full, no way to stretch out. Be sure and walk the isles frequently and wear compression knee socks. I don’t care your age, do so. You’ll be very happy in BKK. If there are any delays etc. the trip gets even longer. I go from BKK to the northeast after a night in Bangkok. Either drive6-7 hours or catch another Thai flight. Even then for me it’s another hour of travel.
if just changing dates it’s 50$ American Air. Unless your a club member or flying with the best ticket. Unfortunately you don’t have time to get a airline charge account. I have American, but others are available. My son used United. Accumulate some nice air Mike credits too.