The immigration website seems to be down (https://extranet.immigration.go.th/fn90online/online/tm47/TM47Action.do produces an error: No backend server available for connection: timed out after 10 seconds or idempotent set to OFF or method not idempotent.) and immigration cannot be reached over the phone or hotline. Anyone has any idea what's going on there? 

Immigrations extranet has been down for over 2 weeks now. Every site on it is down.

Many topics have been posted about it and in the pinned topic the last 4 or more pages of it are discussions about it.

Continue the discussion here. https://forum.thaivisa.com/topic/812263-online-90-day-reporting-available-from-april-1st/

This topic now