Last heard, you can get a Thai validation on your "current license" through them to fly their aircraft. The cost (quite a few years ago) was 500baht.
Not sure of the processing time but do not expect to turn up on the day, unannounced, and fly. Of course you can take one up with an instructor with nil Thai validation.
Considering Hua Hin's policy and the current political situation, even if you did pay and wait to get a VFR Thai validation, they would most likely NOT let you take an aircraft solo - you'll have a minder.
Hope this helps