Complex sentence: There is only one active Indonesian spy organisation in the town known as "Gerakan Ekonomi Melayu Indonesia" (GEMI) frequently engaging relations with Indonesian communities living there to contribute information for Indonesian commandos until the bombing of the MacDonald House in Singapore.
Split into simpler sentences: There is only one active Indonesian spy organisation in the town, known as "Gerakan Ekonomi Melayu Indonesia" (GEMI). They frequently engaged with the Indonesian communities living there to contribute information for Indonesian commandos until the bombing of the MacDonald House in Singapore.