"Airlines are attracted by the 737 MAX 8's lower operating costs and fuel efficiency," BOC Aviation managing director and chief executive Robert Martin said in a statement.
"We are delighted to announce the inclusion of these additional aircraft as we build our future delivery pipeline."
BOC Aviation, owned by Bank of China (HKSE: 3988-OL.HK - news) , is based in Singapore with offices in Dublin, London and Tianjin. It is a key customer for both European aircraft maker Airbus and its US rival Boeing.
BOC Aviation said its fleet is leased to 68 airlines in 32 countries as of end December last year.
Following the latest purchase agreement, the company said its cumulative outstanding orders, purchases and deliveries from Boeing total 331 aircraft.
Most of its Boeing planes are from the single-aisle 737 family, a popular choice among low-cost carriers, which have expanded rapidly in Southeast Asia.