This phrase: คุณ ไป ที่ไหน ที่ ประเทศ ไทย ครับ

Is translated to: Where have you been in Thailand?

How does this end up being past tense?

Because there is no ja before the bai to indicate future tense.

There is no gamlang before bai to indicate present tense.

I think you need to be a little clearer here. When you say past tense, is it the past simple you want or the present perfect? Or something else altogether?

Because there is no ja before the bai to indicate future tense.

There is no gamlang before bai to indicate present tense.

I don't entirely trust the first to eliminate future time reference, and the latter definitely doesn't work. If it has to have past reference, that will be from the context. There isn't enough information in the post to choose between simple past and present perfect; indeed, in the right context, it could even require the pluperfect tense when translated into English.

Its past tense because you say it is, or the person who wrote the original said so. You must know the context to make sense of most basic language.

As you know it says: You go which place in Thailand ครับ . It is as clear as that.

Its past tense because you say it is, or the person who wrote the original said so. You must know the context to make sense of most basic language.

As you know it says: You go which place in Thailand ครับ . It is as clear as that.

I agree, this is not necessarily past tense. It all depends on context.