Buying iphone from thailand?

If i bought from istudio thailand should i pay the vat for airport or istudio?
or can i brng my phone as my phone without paying vat?

You pay the full price of the phone at Istudio. You will apply for your refund of VAT at the airport upon departure. So it is advised to get to the airport early.

To read more on VAT just goggle. VAT refund Thailand instead of asking questions and maybe getting bad information here.

Standard method is to pay VAT at the retail seller store and then take that receipt to the VAT return office in the airports to get the VAT back to you. The Internet will give details.

You can bring in one personal telephone into Thailand as your personal property with no intention to sell it in Thailand, and take it out upon departure. Likely the Green Line will not even want to deal with one personal phone.