Can I take out $20,000 from my thrif tplan? I am 69 plus without any withholding taxes - my plan saying they will withhold $1000 forfirst $10000 and $2000 for the next $10000.

How much total is in the plan.
What are the terms of the plan, and who runs it.

Taxed event probably and the company withholds for you. How much did you put in vs. gain?

Without knowing the nature of this thriftplan (is it a 401(k), a tax deferred plan or what). Its hard to give a definitive answer.
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If it is a tax deferred plan, then you will owe taxes on any withdrawal from the plan. So the plan may be required to withhold part of the distribution against your tax liability. When you file your tax return for the year the taxable portion of the distribution will be included in your income and you may get part of the withheld amount back then.

I suspect the OP is referring to the federal Thrift Savings Plan, which is the federal equivalent to a corporate 401K plan.

He clearly IS allowed to make a $20,000 withdrawal, but he cannot avoid SOME withholding for federal income taxes. The $3,000 figure cited appears to be about the right amount, but I cannot say for sure until I find out what other sources of income he has.