Public display of affection is frowned upon in Thailand. Though you may see couples hugging, kissing, and holding hands in public, a girl from a good family most likely would not do that. Of course, Thailand is not a country where you can get arrested for hugging your girlfriend in public. But due to the Thai dating culture peculiarities, she probably wouldn't be happy if you try to kiss or hug her in the street or in any other public place. So save that for the moment you are alone with your Thai girlfriend.