I participated in a panel on Informal Markets and Peacebuilding in North Korea at the United States Institute of Pace last Tuesday where we discussed remittances. There is no data available on how much remittance North Korea receives since the country does not publish remittance statistics.
However, remittances are being sent from South Korea and China through informal channels (hand carried to the border by informal operators or wired). According to the Ministry of Unification in Seoul, North Koreans living in Seoul remit around 10 million dollars per year. Other estimates indicate that the annual amount is within the range of $5-$15 million per year.