Can I still play LoL even if I switched country?

When creating an account, player must choose a server on which wants to play (usually the one whose server belongs their country). Once created, this belongs solely to the server in which was created, and the login credentials are not valid for other servers.

In order to play with the account in another server, that is, to transfer it to another server, transfer can be purchased in Riot Store of the PvP.net client, on the tab "Account".

Generally, transfers to another server costs RP 2600. RU, TR, BR, LAN and LAS servers does not have the possibility of transfer to some servers. Currently, is not possible to transfer from or to servers SEA and KR, the first one because the server is hosted by 3rd party Garena, and the later one due to be available only to users in South Korea.

You actually HAVE to continue playing on the NA server if you don't make a new account, unless you buy a transfer. EDIT: Just realised, three years later, that Singapore is part of the SEA group of servers and so is run by Garena, meaning accounts from other servers can't be transferred at all.

Playing on a server a great distance from you will have much higher latency and will cause "lag".