The hell trials can boost your stats depending on whether you take the good or evil path.
The machine of Lum the Mad in Watcher's Keep can boost each stat by one point.
The Deck of Many Things can boost one stat depending on your character class. (Str for warriors, Dex for rogues, Wis for divine casters, and Int for arcane casters. Not sure how dual or multi classes are handled.)
The very last part of the game is the throne of bhaal battles. The deck of many things is in WK but there's no reason not to get more specific with the information as the lack of "don't spoil" or any other marking indicates the OP was looking for specific information.
Look, Man, I'll give you a day to go get some rest, have some coffee, whatever, and re-read the initial post.
after which you can delete your last post and we can both pretend you never made it. The hell trials are the five tests of virtue you do before finally fighting Irenicus in hell. One of these tests is a confrontation with Sarevok, where he challenges you to become angry. Comply (evil path) and you get +3 strength or somesuch. That's a stat increase, isn't it? That's WAY before the ENTIRE ToB section of the game, isn't it?
Title of this topic: "Are there any opportunity to increase stats in SoA or ToB"
Now, would you like to tell me how the end of SoA is at the very end of the SoA + ToB package? It's at the end of SoA but it's not at the end of "the game" by a long shot.
Spidey's post was... why is it still there? So you too believe that the SoA endgame happens after the ToB endgame?