well basically, the difference is tha i thought is just the simple past form of the ver think .take a loot at this : think (present) thought (past). that is it. example: i think you are a very good student. (present) i thought you were here last night (past). about guess and suppose. it is quite the same. you can use them with the same purpose. you use it when you are not sure about something. example: we are going to travel to cartagena i guess i going to be fun . bye take care i hope you solve your doubts .

Mostly between I think and I thought.

The main difference between guess and suppose is this. When you guess you may not have an idea what the answer may be. Generally, when you use suppose, the intimation is that you have some idea of what the answer may be. Of course, if you make an educated guess, you would have some idea of the answer. It is a slight difference but mainly depends on the context.

I thought the weather is nice to go out I think we should go to a date I guess you will accept my invitation I suppose your answer will be "Yes"