Since late last year (2016), all Chiang Mai Immigration services had moved to Promenada Mall whilst long awaited demolition and rebuilding commenced on the Airport site.
Promenada services have improved out of sight since the partial move of 2 years ago which saw very long early am queues and too many grumpy old men getting wound up over document* requirements. *Mostly self-induced.
The new sub offices eg Lamhun, have taken the strain off CM which has become far more efficient anyway. They ditched that personal info form pretty quick too ... no means of data storage/retrieval other than on paper.
If one arrives early, say 0700 (not 2am anymore) you'll get a visa extension slot for the same day.
I have only done 1 x 90 day report in 2 years and walked in at 11am to be served not long after but that was an exception rather than the rule.
I also choose to use an agent to process my extension/re-entry rather than arrive at 7am and be there until late afternoon, cost is 3,500 for G4T fast track service and usually means depositing docs with them (office also in Promenada) before lunch and returning at 3pm to collect stamped Passport. That's for Retirement, Marriage requires your return visit a month later for stamp(s).