Best AmEx card for:

A Thai friend, now a US citizen, travels to Bangkok from SJC several times a year.

What's the best AmEx card for earning enough air reward points for a free flight? Could be business or personal. Card would be used in Thailand to shop, and for cash advance. Could be used in US for business expenses, rent, utilities, ... (I don't know how much could be charged annually.)

Air reward availability also matters. A card limited to one airline? Or membership points - flexibility? availability?

AmEx preferred because of general acceptance in Thailand.

Sylvia