My assumption is not that Trump was admitting to being a flight risk by his TS post [View all]
My assumption is one of a number of things or combination thereof led him to create that post that has to have his lawyers bashing their heads against a wall repeatedly:
1) He is embarrassed by that fact that everyone will be able to say 'Trump is out on $200,000 bail' because it sounds bad. $200K bail is indicative of major crimes. He wants to reframe it from 'indicative of major crimes' to 'they stupidly think I want to run away'.
2) Alternatively, he's calculated this move is going to wind up with him being slapped with an ankle bracelet (and frankly, it should). And he actually welcomes that, and I can come up with about 5 reasons why he might, #1 of course being fundraising, #2 being 'see, ELECTION INTERFERENCE!!' and I could go on with other angles along these lines.
3) He's really not as rich (or at least wealth is not liquid) as he makes it out to be, and $200K is actually a lot to him and/or he hates the idea that he has to hand over so much to the Court because it won't earn him interest. Obviously this implies that he's such an idiot that he thinks he has a shot at getting it reduced by ridiculing the DA over the idea that he would flee.
4) He is such a pathological narcissist with such a profound and deep need for constant attention that he made this post KNOWING it would result with endless chatter on the Web, and his face and words being talked about on the TeeVee for a couple days.