That is not about countries but about places. Places which have extremely low density of population. Even if you go to like Nigeria and then somehow appear in savanna, your presence will likely be noticed on your way. Your body is likely to be eaten by hyenas or any other scavengers. But again, this should be a remote area. They won't be able to find and identify you however it does not mean you won't be identified years after. The degree of decay (if anything will be left) will show how many years approximately passed and they will check who was missing at that time.
If you have a boat and a remote area, that's much easier. Enough to tie yourself to the boat, make some holes and it will sink in a few hours. A metal boat of course, metal does not float in the case we described before. Poor countries won't even send a rescue and search team. But should be far from the coast.
Mines abandoned long ago. A lot of job because you need to cave in the tunnel somehow and isolate yourself from the outer world. Very dangerous, hard to breathe, no information about explosive gases. Mines can be flooded or removed without checking what is inside.
Chernobyl zone. Is controlled so entering must be unnoticed. Entrance to the cellar can be blocked by making obstacles, reconstruction of the city is unlikely in the nearest tens of years. Diggers won't go the place which is under debris. Cellar of a regular tower block is not too interesting.
Remote Siberian forests. Same with Alaska. Thousands are never found.
Make sure that you can get out if you failed or decided not to CTB. Two diggers have been stuck in an elevator shaft of abandoned house for a week drinking their own wee before accidentally rescued.
If you are ever found and identified, you can be 100% sure your parents will be notified.
But do you really need this? Your parents will live with faith that one day you will appear, they may waste a shitload of money and time to find you... Some operations take months and years. Rescuers will waste a lot of time dealing with just a suicide when they could be find a person who is a victim of human trafficking and who may be still alive.