Sorry but many of the comments are rubbish. It’s not the number of times. It’s the pattern and abuse. Some people like me have entered visa exempt more than 12 times in a year. but each time I leave the country for 7-10 days. Then there are people who come max out and get an extension then leave for a day and repeat. And repeat again. Then you could have a problem
what is they way I learned from Thai people is this and it usually works, but not all the time. Look interested in what you want to buy and after some time ask how much and ask can lower price. They usually give me something significant