"Finally!": Thai grammar - 'sĭa tee(เสียที)' and 'sàg tee(สักที)'  

Thank you 🙏

I guess nai tisut is expressing state .but those words express states and feelings

I apologize for the confusion. "สัก" (sàg) literally means "just" or "only," so "สักที" (sàg tee), as in the dictionary means "once." When you say "เปิดประตูสักที" (bpèrd bprà-dtoo sàg tee), it gives the sense that you want someone to open the door, but they were just occupied with something else and wouldn't open the door yet. So, you can't wait any longer, and you ask them to open the door just once for you because you need to go out or it can convey the meaning of "eventually." Adding "สิ" (sì) to give the command sense that you need the door to be opened now. "เสียที" (sĭa tee) and "ในที่สุด" (nai tee sùd) convey a sense of "finally," but you can notice that "ในที่สุด" is commonly used at the beginning of the statement, and "เสียที" is used at the end. For example, "We finally arrived" can be said as "ในที่สุดก็มาถึง" (nai têe sùd gâw maa tŭeng) and "มาถึงเสียที" (maa tŭeng sĭa tee).