Generally, to get a 30 day extension of stay based on tourism, you need the following documents:
1. Your passport and:
a. a copy of your data ("picture") page
b. a copy of your most recent visa (if you have one)
c. a copy of your most recent stamp
d. a copy of your departure card
2. A TM30, filed in the immigration office.
3. The forms (each immigration office may have different forms, and want to use their special forms)
4. 2x passport pictures
5. 1,900 THB.
Each immigration office can include additional paperwork or documentation. You should contact Prachuap Khiri Khan immigration office (where Hua Hin is located) at
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for more information about their specific requirements.
I don't know if their website is up-to-date though.