the fourstrokes do 12.5 ( CBR 150) they are " normal " Thai street bikes. Thats why they are so popular over there. Same goes for Cycle Cross , which is the common form of Motocross. (110 scooter class and 150 fourstroke class)
This are the most popular form of racing in Thailand , Malaisia , Indonesia and Philipines. ( A bit like Holden V8 in Australia)