Both Nick and Andrew of New Mandala have a new post on PAD Strategy. They look at 4 possible endgames and what is on the PAD's mind. I have briefly summarised/paraphrased the 4 below:
(1) For the king to step into the fray and asks, to guarantee national “reconciliation” among other things, that Samak resign and is replaced with a compromise Prime Minister.
(2) Elements within the PAD may hope that an escalating confrontation could motivate an army faction to mount another “extra-constitutional” intervention: a coup.
(3) The PAD may, more modestly, be hoping to de-stabilise the Samak government sufficiently that its management of the economy and society is brought into further disrepute.
4) Elements within the PAD may also be hoping that a heavy-handed government response to the current protest may provide them with some politically useful symbols of repression (and perhaps even some martyrs) that could be used to invigorate future phases of their campaign.
BP: For (1), the PAD's problem is not with Samak, it is with "Thaksinocracy" (i.e that Thaksin can win elections and that rural people are allowed to vote). Any replacement from PPP will be called a puppet of Thaksin. I am sure the PAD would also turn on Banharn as well if he was to become PM as he also favours amending the Constitution. I really don't understand how this option helps restore "unity" (which is a mere fantasy anyway, but that is a post for another day) as PAD won't be satisifed with the answer of an elected MP as PM. An unelected MP as PM is unlikely to help either if they are subject to control by the current members of the legislature. The coalition has the numbers even if some figurehead is PM. PAD will only be happy if there is no elected parliament. They want to revert to the 70% unelected/30% elected option as it is the only way they will ever hold power.
I think (2) is the the most unlikely and I think it was more hope on PAD's part. Samak and Anupong seem to have a good enough understanding and by all accounts Anupong will continue in his role as Army C-in-C. The Manager today has an expose on the close relationship between Samak-Anupong - no real details or substance, but the intention is clear and that is to criticise Anupong. This is not the first attack on Anupong by The Manager and is unlikely the last.
I think (3) and (4) were the PAD goals that they thought they could realisitically achieved. The problem is they lost the media war in the beginning because of their raid on NBT and how they raided NBT. I think it is likely that some members of the government/security forces had some information, but they couldn't arrest anyone in advance - can you imagine the uproar if they had arrested the 82 before the raid? PAD gambled that the police wouldn't arrest the 82 but they managed to do to arrest them before the PAD reinforcements arrived and the whole plan went astray. I think this was helped as some in government had an inkling on what was going on and decided that catching them in the act was the better option.
I think that PAD underestimated Samak and assumed he would immediately crackdown on the PAD, but Asia Sentinel offers an explanation as to why Samak didn't:
Samak told foreign journalists Tuesday that he would starve the protestors out rather than use force against them. This was a result, he said, of an audience he had with King Bhumibol Adulyadej, who told him to “enforce the law with extreme caution” and to be “soft and gentle.”
The utterances of the king carry strong weight in Thailand and these words can be interpreted as a continued royal endorsement of the Samak government.
BP: Needless to say this also helps a certain mythology....

I am amazed that the Samak metion of the audience has not been widely reported. It has been known about for some time. Samak did give the interview to foreign and not Thai media and one would assume it is not a lie by Samak for very obvious reasons but it still seems to get rare mention several days after the fact.
Interesting
occasional poster
Add in state of emergency is declared and army units take to the streets but dont act as Anupong thought and I think you have another possible scenario.
Keeping troops in barracks makes it a lot easier to control them
occasional poster
Out of all this, the person who surprise me most is cool-head Samak.
I was darn sure he should have hurl a SAW and personally lead the crack-down by now. Seem like I underestimate him...
It is interesting how one wrong move actually turn the tie.
1. Possible, if that compromise figure can be Democrat. But I don't think it is likely.
2. It is possible, as long as Samak keep cool head and nobody on his camp slip up in the heat of the moment, they will be ok. If there are violence, military may change their mind.
3&4 seem to be more possible. It is difficult for PAD to have a clear victory on this crisis but they can always use this as their stepping stone. But IMO, Sonthi is the key for PAD. Nobody can convince the mass like him. Without him and his ASTV network, it would be much more difficult.