Not sure where to post this as the section for Thai & visa stuff is very quiet & this place is very a fountain of knowledge.

Do Thai nationals need to fill out the white departure card for immigration at the airport when flying out of Thailand anymore?

I've seen dates ranging from the 16th September to the 1st of October of this year but so often officialdom fails to implement changes in time & the old systems remain in place.

The system for Thais was supposed to change on the 16th Sept & for non-Thais on the 1st October.

If in doubt just fill it in, and they can throw it away if not needed. That form really isn't a big deal.