We can use Prague (my home base and most expensive of the eastern cities) as a comparison to Bangkok. The cost of living is almost the same, it's safer, and less corrupt as well.
As for cost of living, I really don't know... I was basically just a tourist, but remember it was $1500/month for a nice 2 bdrm apartment in the city center. It was a really nice place, but I can get far more in Thailand for $1500. Then again, if I was setting myself up long-term, left the city center, and signed a 12 month lease, I'm sure I could have gotten better value.
If you continue eating the same Western style foods, grocery bill would definitely be cheaper out there than in Thailand. You can eat on the cheap in Thailand, but that gets really tiring really quickly. Then eating normally is more expensive than any Western country, due to the import tax.
Again though, can't say anything bad about Prague. It's a great city. I don't know if I'd classify Prague as Eastern Europe though. That's more Central, no? It's definitely a world apart from the other major cities east of it. Even just when you're on the train, it's obvious when you cross the border from Slovakia into Czech Republic. There's an immediate difference, as if everyone all of a sudden got 3 times wealthier. That's the whole reason they broke the country into two. Everyone in the Western part got sick of paying for the Eastern part (now Slovakia), so they kicked them to the curb.
Living in Prague I could easily do, but there's not a chance I'm heading out to Kiev or Bucharest to setup a new life as a foreigner. And I'm sorry, but there's no way Eastern Europe is safer than Thailand. Unless you're an egotistical prick with an IQ of 30, it's very difficult to get yourself into trouble here. And if you do, you more than likely did something to deserve it. Whereas in Eastern Europe there were several times I felt threatened, and in a situation I shouldn't be in. Almost got thrown out of a moving train once, as five guys shook me down for money. Cunts.
Corruption -- I don't know, that's a weird topic to debate. For example, remember a while ago when the Hungarian government came out, said they've been cooking the books for a couple decades, and the country is actually twice as much in debt as everyone thought? Then mass riots ensued?
Couldn't find stats on homeless rates, but you're going to have a hard time convincing me that there isn't as many or more homeless people in Thailand.
There's no homeless people in Thailand. Well, there's loads I'm sure, but for the most part they all live at the temples, and you never see them sleeping on the streets. It's one of the benefits of living in a Buddhist country.
Anyway, this is long enough. Love Prague, but can't see myself going east of it.