Question

i think so 和 i thought so 有区别吗

Answer 1

有区别，两者区别是时态的不同
区别一 think 和though时态
think的过去式和过去分词的形式是thought, 所以区别是think用在一般现在时，thought用在一般过去时，意思都是思考，认为

区别二 常见句型
I think you are very brave.
我认为你非常勇敢。
Women used to think they were on the shelf at 30.
过去女人一到30岁就认为是过了结婚年龄。

His thought is beyond the reach of my imagination .
他的思想不是我所能想象得到的。
This fable arouses in us thought as well as laughter.
这个寓言不仅引我们发笑,而且还能启发我们的思想。
We now find ourselves much closer to the working people in thought and feeling. 我们现在感到在思想上和感情上和劳动人民接近多了。
区别三 常见搭配
think about
think ahead
think aloud
think back
think of

at the thought of
collect one's thoughts
read sb's thoughts
second thought(s)
train of thought

Answer 2

有区别。口语中常用 I think so，表达观点。
thought 是 think 的过去式，
而 I think so常用于对话中，故不用过去式，用现在时。

Answer 3

I think so. 我也这样认为
I thought so. 我也曾这么认为
一个是现在时，一个是过去时

Answer 4

单从时态来看 think是现在时 thought过去时或过去分词，用的语境不一样。
要结合语境和时态来用。