Previously I found a useful post on ThaiVisa about Free (30 hrs/month access for existing ADSL accounts) True Wifi Promotion for True Online Customers (archive link below - so cannot reply to that thread)..

** Question: - does this still work for existing users? When I tried to logon after several months not using it I get the message my ID isn't recognized. Anyone else still using it? it used to work until end of last year.

An archived topic http://www.thaivisa.com/forum/topic/654623-free-true-wifi-promotion-for-true-online-customers/#entry6625859

Ok, got through to True eventually. They ended the service end of Jan-2015.

Brilliant.