@Hal65
On 18 April you posted, apparently from Pattaya, in the topic Can I fly on a new passport without moving my old visa?
On 30 April you posted, (from Pattaya or Chiang Mai?) in the topic Central Festival immigration questions
On 18 July you posted, from Chiang Mai, in the present topic Passport stuck at embassy as checkin nears
You have given no dates but some approximations, in chronological order as follows:
On or before 27 June, you got what you refer to as "a 90 day checkin" stamped into your passport, presumably at the Chiang Mai immigration office.
On or before 27 June, you sent (mailed) your passport to the US embassy in Bangkok, presumably from Chiang Mai, apparently with an application for a new passport.
on 27 July, your current permission to stay will expire.