Thrift Savings Fund Improvement Act - Requires the Federal Retirement Thrift Investment Board to: (1) study the operation of existing precious metal funds to determine the best practices of such funds, (2) establish the Precious Metals Investment Fund incorporating the best practices of existing funds, and (3) make such Fund available to individuals participating in the Thrift Savings Plan. Requires that contributions to such Fund be invested in physical gold, silver, or platinum bullion.