I'm a Sri Lankan citizen currently living in Russia. If I travel from Vladivostok to Seoul (S7 airlines) and within 24 hours from Seoul to Colombo (AirAsia with a transit in Kuala Lumpur), do I need South Korean and Malaysian visas?
A query in TIMATIC, the database used by airport check-in staff, gives the following:
For Malaysia, assuming Seoul-Kuala Lumpur-Colombo is in a single booking, you do not need a transit visa if you have a South Korean visa. If you don't have one, you do need a transit visa.
For South Korea, assuming Vladivostok-Seoul is a separate booking, you do not need a transit visa if you don't have checked-in baggage. If you have checked-in baggage, you do need a transit visa.
UPDATE: Get a South Korean transit visa, and you will be 100% covered.