What you need to have
Thailand is a beautiful country with a lot of modern amenities at hotels, restaurants, resorts, etc. What might be missing from the bathrooms are toilet paper and hand soap. I'm not sure hand soap is common in Thailand. When I asked locals at the convenient stores and shopping malls for hand soap most people were clueless to what I was referring too. Some people would just take me to the hand sanitizer. Please take note that I don't speak Thai, didn't have a translator or used a translator app on my smartphone. When I finally found hand soap I only saw a few brands. Regards to the toilet paper you might be required to buy some from a dispenser. If they don't have toilet paper don't be surprised to find a bidet shower spray on the toilets which comes in handy if you don't have any. The bidets on the toilets might explain why some places don't give complimentary toilet paper to the public. Doing some reaching online people gave a few explanations of why bidets are widely used in Asia. The two that stick out are, low water pressure (flushing) and narrow pipes (plumbing). I reached out to someone from Thailand to cleaner things up on why Thai people use them. The person stated that Thai people think it is cleaner compared to using toilet paper.