I lived in Malaga 2000-2006 and have NIE plus the old red residencia card. I worked as a teacher for 1 years and have a social security record.

I now wish to live in Spain again as I am 65 but living in Thailand. My full UK pension commences in May 2021.

The covid rules mean that I can fly out of Thailand to secure my residencia (I think), but I must quarantine ONCE they open Bangkok to expats. So it could be 4 months to ship my furniture, or more. I don't have a genuine Spanish address yet.

Can I take my NIE and Passport to the Bangkok Spanish consulate to get my permanencia? I think I must sort this out in the next 28 days!

Eddy

I don't know about Spain but - under the Withdrawal Agreement, a person who has acquired permanent residence rights can live outside that country for up to 5 years before losing their rights.

Article 15

Right of permanent residence

1. Union citizens and United Kingdom nationals, and their respective family members, who have resided legally in the host State in accordance with Union law for a continuous period of 5 years or for the period specified in Article 17 of Directive 2004/38/EC, shall have the right to reside permanently in the host State under the conditions set out in Articles 16, 17 and 18 of Directive 2004/38/EC. Periods of legal residence or work in accordance with Union law before and after the end of the transition period shall be included in the calculation of the qualifying period necessary for acquisition of the right of permanent residence.

2. Continuity of residence for the purposes of acquisition of the right of permanent residence shall be determined in accordance with Article 16(3) and Article 21 of Directive 2004/38/EC.

3. Once acquired, the right of permanent residence shall be lost only through absence from the host State for a period exceeding 5 consecutive years

On that basis, if you've lived outside of Spain since 2006 you would have to start from scratch as if you'd never lived there. Which I guess would mean being physically in Spain before the end of transition.
Unless anyone knows different, I think you might need to get your ass back there asap.

Yes, the OP must be in Spain before the end of the transition period to start a fresh residency application. Under the pre-Brexit rules, permanent residency expired after being away from Spain for 4 years IIRC.

^^ 12 months not 4 years

A limit of 12 months absence for permanent residency rights would be very draconian.
Most countries have different permitted periods of absence depending on whether you have acquired permanent residency rights or not.
Normally, if an EU citisen has lived in a country for a continuous period 5 years and thus acquired "permanent" rights, they're allowed to be out of the country for several years without losing their rights.(In France it's 2 years).
During their first five years of residency, spending a year outside the country is normally classed as an interruption to their continuity of residence, so the clock would be reset when they go back.

Go onto the CAB Facebook page, they are the Citizens Advice in Spain group and all the correct and up to date information you need can be found there.