If your payments are through a credit card like subscription or buying games, yes your region has to match. So if lets say you are using an american CC and have an american account...as long as that CC is active you can still purchase as normal, it doesnt matter if you changed countries. Because your PSN account is tied to a payment method that has to be from the same region.
But if you move to another country, and you end up closing the bank account from there and opening a new local one, your region wont match anymore. But its an easy loop. Either open another account in the local currency and address and bank you are in next, when you buy a game all you have to do is switch back to your original PSN and can play it there and continue collecting trophies for it there. Or even easier, f the bank just buy digital cards on like play asia etc. I changed 2 countries and thats all I do, dont even bother with credit cards anymore.