Thai immigration appears to be inconsistent about the requirement to complete this part of the form. Some offices say it is optional. Some offices don't ask you to fill it out at all. As far as I know they aren't asking tourists to complete it when they arrive. It seems to be only for foreigners staying long term. Time will tell whether or not they ratchet up the requirement for all foreigners to complete it.
FWIW, I was in Thailand a few weeks ago (no visa, it was a relatively short trip) - I did not see this question on the immigration form.
I just ignored them. Nobody bothered to ask. Seems optional to me.
Also its Skype, Linkedin and Facebook if i remember right. I dont have those.