For those guys looking to do 90-day reporting here at Chiang Mai immigration on 22 July, you MUST use the drive through. Yes, you can walk through it.
This is because those services are moving to the Promenada location. To my knowledge, the 90-day window at the main office by the airport will remain open for vehicles only after tomorrow.
Not sure if volunteers will be at that location or not.
TLDR : Answer Summary
If you're doing 90-day reporting at Chiang Mai immigration on July 22, make sure to use the drive-through service. Walking through is allowed, but services will be relocated to the Promenada location soon. After July 22, the main office by the airport will only accept vehicles.