I don't know what a "Thai Prenup" is, so I may not be giving you a fully-informed answer.
Assuming, eventually, the prenup possibly would be enforced or contested in an American court, then it would probably be best to have it crafted under American laws. If you anticipate the agreement may eventually be needed in the Thai legal system, then it should probably be crafted with an eye toward those laws and norms.
Prenups from other lands usually are valid and enforceable in the U.S. -- so long as they satisfy the requirements of the laws of the particular state in which they are enforced or contested. There is nothing magical about a document prepared on American soil as opposed to Thai soil. Sometimes, however, cultural norms from other lands conflict with public policy that is common in the U.S. When that happens, the agreement is not enforceable (in the U.S.).
Given that the technology allows it, why not have an agreement prepared now, in the U.S., e-mail it to her for review and allow her time to contemplate it's import and seek counsel, revise it if necessary, and then execute the document . . . wherever?
(213) 394-4554 x0 Mr. Shusterman is a former INS Trial Attorney (1976-82) with over 35 years of immigration experience. His response to your question is general in nature, as not all the facts are known to him. You should retain an attorney experienced in immigration law to review all the facts in your case in order to receive advice specific to your case. Mr. Shusterman's statement above does not create an attorney/client relationship.
There is no way to know which form of pre-nup will hold up better. It will depend primarily on where you intend to live permanently. You should decide before marrying/. Both of you should have lawyers. And do NOT have different documents prepared for each company as they could end up competing with each other.
It's not where you are getting married that's important given your choice of Country pre-nup question: it's where you might end up getting divorced. Where do you intend on permanently residing? That's the Country to have the pre-nup drafted and executed.