(Reuters) - The head of Indonesia Stock Exchange resigned on Friday after index provider MSCI flagged a possible downgrade to "frontier" market status, triggering a more than $80 billion market rout. The rupiah was last at 16,800 to the U.S. dollar having set a record low of 16,985 last week. "I hope this is the best decision for the capital market. May my resignation lead to improvements in our capital market," he said. Foreign investors sold around a net $645 million worth of shares in the two-day selloff, exchange data showed.