I have a non-o "retirement" visa.

I last entered Thailand on the 10th Oct '15 and am booked on a flight out on the 7th Jan '16.

This makes it exactly 90 days in LOS including day of entery and departure.

Am I going to have a hassle at the airport?

Reports are not due until you stay longer than 90 days - so leaving exactly 90 days from previous entry would not be an issue - remember day of entry counts as day 1 of that 90 day count (as believe you did from your post).

No.

Assuming you have an extension of stay based on retirement and entered the country using a re-entry permit you do not need to make a 90 day report if you are leaving on the 90th day.

If you entered using a non 'O' visa then 90 day reports are not required as you have to leave on or before the 'admitted until' date (90th day) or apply for an extension of stay.

A non immigrant O-A (retirement) visa entry (which may be what he has) is for one year and indeed would require 90 day reports if staying more than 90 days.

7 JAN is the 90th day (maximum stay with a standard Non O e.g.).

Literally the report is about "staying longer than 90 days".

No prob.

In any case: no check at the airport about 90 day report.

Edited December 24, 201510 yr by KhunBENQ

I have a non-o "retirement" visa.

Do you mean you're non-imm O or a non-imm O-A or an extension of stay based on retirement?

If you have done 90 day reports before, it would have been on the non-imm O-A or the extension. In any event, airport immigrations aren't concerned with 90 day reports, only over-staying your permission to stay or extension of stay.