1. Yes it is safe to bring baby to overseas. However, during overseas trip (depend on locations) it is best to purchase distilled water and boil them to make milk or water for the baby. However, if you fully breastfeeding then you need not to worry about this.
2. Do remember to stand by Medicine such as fever medicine, cough and flu can be obtained from PD clinic (travel pack medicine). Bring some mosquito patches/repellent. Bring additional clothes for baby to standby.
3. Flight engine sound is quite manageable. During the take-off and landing, let baby suckle on milk bottle/pacifier/latch on to ease the air pressure discomfort in ears.
Do some research on the nearby hospitals/PD in that particular country to stand by in case there is any emergency. In addition, you may want to purchase travel insurance for the baby as well.