Is there a Torah obligation that one has to say thank you for a favor received? Where exactly is that mitzva written? How about asking ‘please’?

Horav Shlomo Miller’s Shlit’a opinion is that there is a most basic mitzva and obligation in our Torah that establishes a number of times, that one has to be and behave as a ‘Mentch’ and follow proper accepted behavior and recognized human values. The Rov maintains that the above is a Biblical mitzva based on the Posuk: “Vehalachta Bidrachav” (P. Eikev) or “Walk in His Ways”. Thanking for a favor done, is also universally one of them.” Saying, please is mentioned many times in the Torah as in; ”Daver No Beoznei Haam” (Please speak to the people) etc.