Can this be done with a TSP?
You can convert a Thrift Savings Plan account to a Roth IRA,
@Joe Schmo, but there's a few caveats:
1. The TSP does not permit in-plan conversions, so-
1.a. You have to be out of the military before you can start converting your TSP, and
1.b. You can't convert your traditional TSP to a Roth TSP.
2. After you're out of the military then you can roll your traditional TSP over to a traditional IRA and do a Roth IRA conversion as discussed in the other posts of this thread.
3. After you're out of the military then you can roll your Roth TSP over to a Roth IRA. If you've had a Roth IRA for at least five tax years before you did this Roth TSP--> Roth IRA rollover, then you can immediately withdraw the contributions you've made to the Roth TSP. (Just like withdrawing contributions to a Roth IRA.) Gains in the Roth TSP have to wait until you meet one of the penalty-free withdrawal conditions.
4. If you have contributions to either the traditional TSP or Roth TSP from Combat Zone Tax-Exempt pay, then you can withdraw them anytime after rolling over the TSP to an IRA. Most veterans leave them in the TSP for the compounding, and some IRA custodians don't want to track the basis of CZTE contributions to a traditional IRA so they'll send you a check for that, but you're able to withdraw them tax-free and penalty-free.
Keep your TSP statements that show what you've contributed to the traditional TSP, what you've contributed to the Roth TSP, and what you've contributed from CZTE pay. Not all IRA custodians track this information.
https://themilitarywallet.com/early-withdrawals-tsp-ira/