CO-CO
Rather wrinkly & occasionally cantankerous member
You do not have to carry your passport now.
A copy of the passport is now accepted.
Pink card is often accepted for hotel bookings instead of a passport.
I cannot say with 100% certainty that "you do not have to carry your passport now". I can say with 100% certainty that I have not managed to find any reference for this 'law' requiring you to carry a passport at all times.
The UK government still tells you to carry your passport:-
Personal ID
Police may ask to check your passport. If you do not have it with you, you could be arrested.Safety and security - Thailand travel advice
FCDO travel advice for Thailand. Includes safety and security, insurance, entry requirements and legal differences.
www.gov.uk
I only take my passport if I am traveling out of province. I always carry a copy of my passport ID page plus latest Immigration stamps.
For hotel bookings I present my driving licence (which is usually OK) - if not, I have picture of my passport on my phone and staff take a photo of that.