What is a good investment choice that will grow my Thrift Savings Plan account without having to put additional funds into it?

So as a general recommendation to all of us, KEEP TRACK OF THESE RETIRMENT ACCOUNTS.

Years ago I left a company, and just left it in my 401K. Then as I got older, and wanted to consolidate things I remembered back to that company, and by that time there had been a merger and then a change of the fund administrator. So by then I'm tracking down a NEW company that moved my money to a NEW administrator.

Last I remember I had left $30K in the fund and by time I tracked it down again it was up to $80K.

OK, so there's that, what I'm getting at is don't lose track of your stuff, and I'd recommend consolidating it (It sounds like you are OUT of the military?) into a civilian retirement account by rolling it over (tax free).

If we are talking about $1700 we are talking about a very small amount of money. It's on par with a single Social Security Payment (probably even less). So again, roll it into something that's easier to keep track of.

Finally...... to answer the question of "where" to put the funds, well, that all "depends".
1) How far away from retirement are you.
2) What are your retirement cash flow hopes
3) What is the totality of all you other retirement funds.

Within those three questions are endless details that influence those factors.

DO NOT put it in a savings account. It is not an emergency fund (as I understand it). You'll have to pay taxes on it. Leave it in a retirement tax shelter.

Now............. from what I can tell, the Thrift Savings Plan has very straight forward investment fund choices. Even better, is they appear to have very good Expense Ratios (the amount that is pulled out of the fund to pay for the management of the fund).

https://www.tsp.gov/funds-individual/

The funds are:
Gov Securities Fund
Fixed Income Fund
Common Stock Fund
Small Cap Fund
International Stock Fund

ALL of the funds carry some sort of investment risk. ONLY the Gov Securities Fund has not lost any money (at the time I am writing this). That fund is composed of short term US Gov Treasury instruments that are LEAST impacted by changing interest rates. It's also going to pay the LEAST interest return over the long term.

I personally have just about liquidated my entire retirement holdings and put them in similar US Gov Treasury securities and money market funds in anticipation of a market crash. Then "hope" to swoop back in the market when it's on it's knees, and put up the extra return on the way back up.

Now, the RISK on my end is that doesn't happen and I spend this time earning low interest rate returns on short term bonds.

Lets discuss (from my opinions)
G Fund - Government short term bonds that are least expose to interest rate increases because the instruments are so short that when rates go up the newer issued short term bonds will be at the newer more current prevailing market interest rates. However, short terms rate are always lower (except in the event of an inverted yield curve, which is beyond this discussion).

Fixed Income Fund - longer term bonds that go over YEARS AND YEARS, but get HAMMERED when interests rates rise. Because a 10 year bond issued 5 years ago for example at 2% is now compared to a 5 year bond issued today at 3% and both those different bonds by a function of math have to now have the same return on principle of the current market rate of 3%, and to do that with the older original 10 year bond is to LOWER THE PRICE OF THE BOND the holder can sell it for today.

My opinion - Interest Rates are rising, and this fund currently has negative returns.

Common Stock Fund - This is composed of US large stocks that follows the Standard and Poor's 500 Index. It goes up and down with the stock market in general.

My opinion - I personally bet my money in this sector, and it will be where I go back to when I am comfortable. I think the market is over priced, and think it's being propped up by COVID economic subsidies. At some point those subsidies will come to a halt and the piper will need to be paid.

Small Cap Stock Fund - Like the large Common Stock fund, but all the smaller funds not in the S&P500. It has higher highs and lower lows.

Opinion - this is even a worse place to be if one is not comfortable with stocks.

International Stocks - This fund is non US Stocks of DEVELOPED markets. So it's a relatively good safe place for international investments.

Opinion - Right now, the world is going sideways and EVERY SINGLE TIME the world goes sideways investors RUN TO THE UNITED STATES FOR STABILITY in investments. Say what you will about the US debt and economy no one else in the world offers a stable economy that seems to always survive and is immune to negative world events. In the event the USA goes sideways and the dollar collapses then where does that leave the rest of the world anyway.

I think international funds are great (I have money in them myself) but they do best when the world is stable and the US stability is minimized when everyone else in the world is stable.

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I said a lot, but what does that mean?

Well, it all depends on how long the funds will be held in a retirement account until you need to draw on them, and how that can be incorporated to your larger picture retirement portfolio.

Where they sit now, dollar for dollar are probably best left in the Thrift Savings plan, BECAUSE you are getting the benefit of the great low expense ratio for the management of those funds. So the question is then WHICH fund to put it in based on your retirement timeline.

Now, if you happen to have a personal IRA account somewhere and you COULD have balances enough to allow you to invest in funds with great expense ratios then I would roll over your $1700 into that just for the sake of keeping track of it easier.

I am a Chartered Financial Analyst (CFA), at one point was a Registered Investment Advisor, and spent much of my civilian career administering/managing the excess funds Credit Unions do not lend out by investing them in the open market of Treasury Bonds and Asset Backed Securities.

I recommend you put it in a savings account for an emergency... unless you already have enough in one.