Bill Heinecke was 42 when he did something drastic: He walked into the U.S. embassy in Bangkok, handed over his passport and renounced his citizenship.

It wasn't a moment of madness, nor was it strictly necessary: The American-born entrepreneur had by then been living and working in Thailand for almost three decades. But it did showcase what he says is one of the most important skills in business — commitment — and, as a result, propelled him up the ranks of the country's rich list.