I'd take small issue with some of what you say here.

Absent further action after the ambiguous bet...
If we ask the player to clarify his action on the first occasion that he makes the error, we can use this as an opportunity to make the rule clear to him and other players at the table, and inform him as to how such a bet will be handled in future. If he's too drunk / belligerent / stupid to follow up on future occasions then we can apply the rule as advised.

The poker table can be an intimidating place and some of the rules / etiquette aren't obvious, especially to new players, and a lot of stuff that they see on TV doesn't help.

The rules are great, but I believe that they should be explained where the opportunity exists to do so without risking the integrity of the game.

You get problems with this type of scenario more often on the turn or river imo.
Preflop, 500 is fairly obvious and standard, but if a player bets say 600 on the flop and 1100 on the turn, and then puts in a 5k chip on the end and says 2, they get held to 200 when it's pretty likely they meant 2000.

How would you rule if the blinds were now 150-300 having just gone up from 100-200, and player puts in 5k and says 5?

5,000. That's the smallest legal bet that can mean 5. Yes, if he said 500 it would be a raise to 600, but he didn't say 500, he said 5.

It's hard to have sympathy in these situations (and trust me, I've been screwed over by them myself both due to my error and dealer error, and in both situations I blame myself for doing what I did) when there is a very simple solution.

If you want to bet 500, say 500, if you want to bet 5,000, say 5,000. If you want to call say call, if you want to raise say raise. Those things aren't hard, and would avoid 95% of the problems on this board.

There is something else I want to address ... the rule applies to ambiguity and times when there are multiple reasonable interpretations of the amount.

and there are times when the action makes it non-ambigious.

Suppose I announce 5 while simultaneously putting out 5 1000 value chips. There is no ambiguity that I might have meant 500. If I meant to bet 500 there is no reason I would put out 5 1000 value chips. So the bet should be 5k even though if I announced 5 without moving chips or moving a 5k chip the rule would apply to make this a 500 bet 9assuming 500 is a legal bet)

Again without context for how the issue gets raised I think this is a raise to 5k. But if the player making the bet immediately objects and there has been no action caused by it, I would have no problem with a Floor ruling it a raise to 600 under rule 1.

Keeping the TDA rule in mind: "whenever the size of a declared bet can reasonably have multiple meanings, it will be ruled as the lesser value."

Can we reasonably think that the player intended to raise to $500? Yes, because the blinds just went up. However, since the legal raise is to $600, I would usually rule it as a raise to $600.

However, other factors might come into play here. Has this player consistently raised small when opening? Does he have other chips in his stack like a pile of $100's and $500's, or does his entire stack consist of one $5,000 chip? Is the player a known angle-shooter?

I could construct a scenario under which I would rule it as a raise to $5,000, but absent a history of angle-shooting or other significant contributing factors, it's going to be $600.

It's pretty ridiculous to punish a player by forcing him to bet $5,000 when it's pretty clear he made a mistake in not realizing the blinds went up. I understand that poker is a game of continuous observation, but this is too heavy-handed to be a reasonable ruling.

How do you know what he meant to do? Maybe he meant to raise to 5k. Would you make it a raise to 600 if he said he intended to raise to 5k? We certainly have not been given enough information to judge his intent.

Perhaps its another player at the table arguing it should only be 600

**** happens. if someone quickly says call or raise and they say they thought the bet was 5k, it's going to be 5k because that's what it is according to the rule.

I can see a scenario where you let it be 600 IF nobody does anything, but in poker, your money is on the line, it is not a good thing to be relying on IFs or somebody else's interpretation. Especially when it's so easy to be clear.

It sucks when the mistake happens and you get burned by it, but that's the only way some people will learn, because that bet will probably be 5k if the next person to act has Aces and acts quickly, so it's probably better to learn that lesson the first time.

If we go back to the blinds being 100-200 (let's call that scenario A) and the same player throws out a $5k chip and says, "five", there is no discussion about intent. It's a raise to 500 according to TDA rules. Even if the player protests and says, "It was a raise to $5k!" we still hold him to $500. I've seen this ruling made and I believe it's correct and within the spirit of the TDA rules.

So why do the blinds going up to 150-300 open the door to asking the player his intent? Why does he get to explain his action in scenario B but his intent is completely irrelevant in scenario A?

To me, it all comes back to the phrasing of the rule, and the use of the word "reasonably". We can reasonably say that the player intended to bet $500.

I'm not a fan of trying to divine intent from a player, but I am a fan of rule #1 - make the best ruling in the spirit of the game.

And I believe they would be correct.

What does action after the bet have to do with this issue? If you're just going to insert events into a scenario to conveniently support your position, this discussion is worthless.

And I don't believe in automatically punishing people for making mistakes. When you punish inexperience, you punish inexperienced players. This is not good for the game as a whole. I hope that's self-evident.

Absolutely not. With the information we have here it would not be reasonable to assume that the player meant to bet $500. I'm not saying there isn;t a possible scenario where we can conclude that the player intended to bet 500. Just that we can't do that with the information we have.

If we are going to make any assumptions (which by the way are different than conclusions) we should be assuming players know the blind level and the be they are facing. If we can;t make that assumption then the came falls apart. The fact that the blinds just went up doesn't change this ..... in fact in my opinion the fact that the player has probably just been told at least 3 times that the blinds went up make it even harder to assume he doesn't know the blinds.

Using your assumptions creates quite a dilemna. Suppose the player in fact know sthe blinds and intends to bet 5k. He also knows the rule .... so he announces 5 and tosses in his 5k chip KNOWING THAT 5K is the smallest legal bet that 5 could signify. But know you come along and say well clearly we should assume that he is not paying any attention to the game and believed that the blinds were 100 200 and therefore 500 would have been a legal bet so he gets held to a minimum raise.

I think the error you are making is you are assuming that the player didn't want to bet 5k and you are therefore working back to justify letting him out of it. But we have no reason to think that he doesn't want the bet to be 5k. Part fo that is because the question was asked badly. Are we being asked what the dealer should default to? Are we being asked what a floor should rule when there is disagreement? Who is objecting? these are all relevant in understanding the context.

Just keep in mind that the information we have is a hypothetical situation with zero surrounding facts and information. Either one of us could easily construct a scenario under which both $500 or $5k would be reasonable rulings.

Here's where we diverge then; I don't feel it's reasonable to assume that a player knows always knows what the blinds are. Particularly if the blinds just went up, and let's throw another assumption in - the big blind has a single $500 chip out in front of him so the amount is unclear. I feel that there are plenty of reasonable circumstances under which an otherwise observant player is unaware of the blind increase.

If he was told 3 times, then sure. It's reasonable to assume that he knows what the blinds are and if that were the case, I would lean towards ruling it a $5k bet. But that information wasn't there in our hypothetical situation.

Absent those 3 reminders - I don't agree with you that it's a fair assumption.

The answers to these questions that I posed earlier would have a lot of influence in my decision:

Has this player consistently raised small when opening? Does he have other chips in his stack like a pile of $100's and $500's, or does his entire stack consist of one $5,000 chip? Is the player a known angle-shooter?

If the answers to these questions are yes, no, and no, then I do think that's it pretty clear he didn't understand that 500 was no longer a legal raise size.

If the answers are: no, yes, and yes, then it's $5k all day.

There are just too many unknown factors that were left out of this hypothetical situation that can significantly influence the decision one way or another. We can go back and forth all day, each of us coming up with different scenarios with different supporting information to sway the decision. It's a pointless exercise.

Now we're on the same page