This morning, I received the following advice by email from the UK Foreign, Commonwealth and Development Office:

Travel advice (2).png

Summary

The FCDO advise against all but essential travel to the whole country.

Still current at: 28 August 2021
Updated: 28 August 2021
Latest update:

The FCDO advise against all but essential travel to the whole of Thailand based on the current assessment of COVID-19 risks.

In addition and for security reasons, the FCDO advises against all but essential travel to:
• Pattani
• Yala
• Narathiwat
• Southern Songkhla province. This does not include areas north of and including the A43 road between Hat Yai and Sakom, and areas north-west of and including the train line which runs between Hat Yai and Pedang Besar.

Consular assistance is available throughout Thailand, except for the provinces noted above. See Terrorism

Source: FCDO