I have recently got a new passport and used an agent to get the stamps transferred. 

You may wonder why I didn't go to Jomtien Im. myself but this is because illness prevents me getting around easily.

Anyway, I thought that transferring the stamps would close the old passport and allow me to update the new one online.

The new pp. came back with a receipt showing an opening date of Oct.24th. with a notify again date of 21st. Jan.

Today I received an email to notify "STAYING LONGER THAN 90 DAYS"  in the old pp.

Do I just ignore this request for the old pp.? and use the new dates for my new pp.?

Yes, you can safety ignore the reminder for the old expiry date. 

 

 

24 minutes ago, monsieurhappy said:

The new pp. came back with a receipt showing an opening date of Oct.24th. with a notify again date of 21st. Jan.

Seems immigration also did a 90 report at same time as stamp transfer. 

Ignore the reminded email you received. 

15 days prior to Jan 21 do your 90 report online. 

Thanks!!