If you are looking for a serious girlfriend, you may have trouble. If you do not speak Thai, most English speaking girls will either be in the bar scene or be well educated. You do not wish a bar girl, so what do you bring to interest an educated girl who may well have a good job.
You may wish to consider online dating or going through friends to increase your chances.
In addition to hua hin, have you considered Bangkok or Phuket?