Hi, I brought my 4 mth old to BKK and I was breastfeeding her on the plane during take off and landing due to the air pressure. As it is a short flight, it was a breeze for us. If you are worried, check on the airline medical assistance should you need help. Pls get a seat at the bassinet area (book early) so that you and baby can get good rest. As long as the baby is well fed and good rest, it should reduce her chance of falling sick.
You can prepare lots of wipes and bring along hand sanitizers. Saline nasal spray may be handy as well. Ensure that your baby will be well hydrated (if you are breastfeeding, shouldn't be an issue). Also, if your baby is using pacifiers, have a few extra ones on hand so that you need not rush to the washroom if one drops onto the floor. Have a safe trip!
Keep the baby warm and breastfeed her when the plane takes off. Keep the baby awake for a few hours before taking the flight, so when you are in the flight, the baby will be tired and fall asleep. Chances are that your journey will pass with baby sleeping throughout. In any case, you must take the medicine for colic or earache.
In addition to the advice above, planes also tend to be super cold. So bundle her up in full length onesies, and carry a warm blanket and possibly a cap as well. My son was ok on take off and landing but many parenting forums recommend feeding the baby so reduce the impact of pressure on their ears.
Keep the little one warm (long sleeves, long pants, socks or tights or onesie)