Leave 4 to 6 hours between a flight on your main ticket and one on a separate ticket at the same airport. On a single ticket 2 to 3 hours is fine because the airline rebooks you if you misconnect. On separate tickets you have no protection, so the buffer is yours to build.
Leave 4 to 6 hours between a flight on your main ticket and a flight on a separate ticket at the same airport. On a single ticket, 2 to 3 hours is fine, because if you misconnect the airline rebooks you. On separate tickets nobody owes you anything, so the buffer is yours to build.
Check the terminal logistics too, because the airport matters as much as the clock. At Bangkok Suvarnabhumi the domestic and international terminals are in the same building, which is easy. Tokyo Narita and Haneda are different airports entirely, and connecting between them means a 90-minute train ride.
One more thing that catches people on side trips: visas. A transit visa will not cover a stopover, and a single-entry visa will not let you leave the country and come back. India is the usual place this goes wrong.