If you have a TSP account and you also have money in a traditional IRA or other eligible employer plan, there are benefits to consolidating your accounts with the TSP.
Consolidating your retirement funds with the TSP means fewer accounts for you to track. Your money is in one place and continues to grow.
Expenses matter because they chip away at your returns. The TSP's administrative expenses are very low and that means more money stays in your account working for you.
After you move the money from your other plan(s) to the TSP, you can make interfund transfers to invest in any of the TSP funds.