I don't have any skin in the game here....I live in Issan and can see the great progress made here when Thaksin was in power eg provision of electricity where there was none, extensive building of hospitals and schools, introductions of pension and health care....radical ideas for a third world country like Thailand, aiming to become a developed nation. I don't think it any coincidence that all progress stopped when Thaksin was the subject of an illegal coup, and it has never recovered...Thailand has gone from an Asian tiger to an Asian donkey.
As to whether he should go to jail? Personally I don't think the trail that condemned him was fair. It was clearly rigged and the sentence given was illegitimate. All people are supposed to be treated equally under the law....Thaksin was clearly not, and neither was Yingluck, and she was a complete travesty of justice.
But the philosophical questions you raise would be very interesting to debate, albeit imponderable. I'd settle for an unbiased legal system that treated defendants equally....and Thaksin was clearly victimised, as Trump is being victimised in the US now where it has been exposed unequivocally that the FBI tried to create an environment where Democrats would win the presidential races and neglected to prosecute Hunter Biden or Hillary Clinton, even going as far to seed cover ups stories for their evil doing. These things happen....I don't care whether Thaksin comes back or stays away. I have to say that I don't think his return is in the best interests of the country....but a destabilising influence and a fall in the value go the Thai baht, would be in my interests as I earn in USDs.
I have never met any nice billionaires, you don't get to be a billionaire by being a good human being, you get that sort of money by breaking laws. I worked at a high level in a very large US corporation and met a lot of very rich CEOs, most not very talented, and by and large, all as$holes. I'm guessing Thaksin fits this mould.
Rather than the man or lady going to jail if they return, I would like to see them appeal, get bail like every other person (even police officers sentenced to death got bail), and then have a totally FAIR, unbiased, non-political and transparent trial.