What documentation do we need for traveling with our grandchildren on domestic flights in Thailand?

When traveling domestically in Thailand with children, the primary requirement is valid identification for each individual. While Thai nationals can fly within the country using their ID cards, it is advisable to have supporting documents in certain situations. Given that the children have different last names from their guardians, obtaining a letter of authority from their parents granting permission for them to travel could be a prudent measure. Though not strictly necessary for domestic flights, it may help avoid complications.