Gambling is indeed prohibited in South Korea, but there are exceptions, such as in Russia. It's banned there too
Russia did not ban prediction market, it is prediction markets (precisely Polymarket and Kalshi) that banned Russia. These two should be differentiated. There are some countries that these two prediction markets banned which can be due to the countries being sanctioned by the United States. Iran, North Korea, Cuba, Syria, Venezuela, and Belarus are also banned.