5 CFR §1650.31

1. (a)A participant who has reached age 59 1/2 and who has not separated from Government service is eligible to withdraw all or a portion of his or her vested TSP account balance in a single payment. Unless the withdrawal request is for the entire vested account balance, the entire vested traditional balance, or the entire vested Roth balance, the amount of an age-based withdrawal request must be at least $1,000.
2. (b)An age-based withdrawal is an eligible rollover distribution, so a participant may request that the TSP record keeper roll over all or a portion of the withdrawal to a traditional IRA, an eligible employer plan, or a Roth IRA in accordance with § 1650.25.
3. (c)A participant is permitted four age-based withdrawals per calendar year for an account.