Tien wrote: “Recently, while I contemplate on Dhamma or a relate subject, even in crowded place (while in the bus, on the side of a street, in waiting room, …), I have no awareness of 5 physical senses at all, totally absorb in the thinking for as long as 30 minutes. Then after I’ve done with my contemplation or a sudden sound happens, my awareness of the senses re-emerged..” and “I know it not yet first jhana..”
It is POSSIBLE that it could be a Sotapanna (or higher) phala samapatti.
It is not necessary to be in a jhana to have an experience like that. In fact, at least in the lower jhanas, one can hear external noises, etc while in the jhana. It is only in jhana samapatti (for lower jhanas) that it is guaranteed that one cannot hear, see, etc.
There is a sutta which describes an event where the Buddha was in Arahant phala samapatti (not a jhana or a jhana samapatti), and did not hear thunder and lightning that killed a couple of people close-by. If someone knows the sutta, please post it.
Also see, “Nirōdha Samāpatti, Phala Samāpatti, Jhāna, and Jhāna Samāpatti“.