1. There will be some sort of a major announcement. A scenario, brought up by a Pheu Thai Party MP, has Thaksin declaring that he has "forgiven everyone" and is carrying no more grudges. He will say that it is time national reconciliation started, but that it wouldn't be possible until one of the key coalition parties makes the first move.
2. There will be a jaw-dropping state-of-the-art video linkage that will make his well-wishers feel as if he were "there" in person. (Imagine Princess Leia in "Star Wars" being beamed up for Luke Skywalker by R2-D2.)
3. A combination of the two: a state-of-the-art link-up in which Thaksin hopes for peace in his motherland.
4. He delivers a shocking speech declaring that he will return to acknowledge his punishment, serve his jail term and then launch a political comeback. (This idea came from an entertainment beat reporter, seriously!)
5. A gigantic gimmick designed to embarrass his opponents, probably in the form of remote-controlled projects related to the economy. Many people believe this could possibly be true because the "big surprise" would be more about substance than form. Moreover, it fits the circumstances when news of the "big surprise" first broke. At that time, Thaksin didn't appear to be in a mood to forgive anyone and told somebody he had called that the Democrats were screwing the economy, before declaring that he had a "big surprise" planned for the country on his birthday.
6. Don't laugh, but actually there are people who think that the first, second and fifth scenarios will take place at the same time. Thaksin, visiting as a hologram, will declare that he has absolutely no hatred left in his heart, then he goes ahead to give the Democrats a good spanking before announcing projects like scholarships and transforming the People's Station (formerly D-station) into a free tutoring channel employing expensive, qualified lecturers.
7. He will become a monk. (We hope this doesn't happen because the last time that an ousted leader in exile took up the saffron robes, it triggered one of the blackest chapters in Thai history.)
There you go. I personally hope it is scenario No 1, but my head tells me it will most probably be No 6. Well, whatever it is, it would still be a nice surprise if Thaksin spends some big bucks on Thailand, no matter what his motive is.