This information is for people travelling on a full ‘British citizen’ passport from the UK. It is based on the UK government’s understanding of the current rules for the most common types of travel.
The authorities in Thailand set and enforce entry rules. If you’re not sure how these requirements apply to you, contact the Thai Embassy in the UK.
Passport validity requirements
To enter Thailand, your passport must have an ‘expiry date’ at least 6 months after the date you arrive and have at least 1 blank page.
Check with your travel provider that your passport and other travel documents meet requirements. Renew your passport if you need to.
You will be denied entry if you do not have a valid travel document or try to use a passport that has been reported lost or stolen.
That's six months, you're best off getting your passport renewed. Getting into Thailand is becoming less easy, especially Visa Exemption - only two entries per year are now allowed with a return home expected between visits
Multiple trips, beyond two or maybr three entries per year are no longer accepted. I was questioned at length arriving 17th November and I am hoping I will be permitted to come back after trip to Vietnam in February, but there's no guarantee