We have a lovely dog called Nam Kaeng (Ice) and when traveling in Thailand by car we almost always take her with us. But finding a pet friendly hotel is a bit difficult. So I added a label Pet Friendly to the accommodation reviews that I did write. If you click on that you will see a list of all the hotels were we did stay with our dog.
But there is also a website dedicated to Pet Friendly Hotels, have a look at Pet Friendly Thailand. Be aware that mentioned prices on this website are not always accurate. I would advice to contact the hotel directly and also check if your dog is really allowed in that hotel. Some hotels accept only small pets / dogs. Most hotels charge a 1 time extra fee for having a dog. And at some hotels that charge depends of the size / weight of the pet / dog.
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