Hello I am traveling to Europe and will transit in Bangkok for 18 hours. I don't plan to leave the airport as I will have 2 young children. Do I need to have a transit visa for this?

From what I gathered is, if you move out of the airport that too beyond 12 hours definitely a transit visa is needed. When I travelled to Europe my layover in Abu Dhobhi was for more than 12 hours. They asked only for Schengen visa. I personally feel once more you must do a small check with airport and airlines authorities.