Verteilung der Muslime in Thailand

This percentage will increase as Malays/Muslims are the only ethnic/religious group in Thailand with a reasonable total fertility rate (just under 2 children born per woman) while the buddhist Thai majority has an ultra-low fertility of around only 1 child born per woman. That’s lower than (far richer) Japan and means that every new generation will only be half the size of the one of their parents. At the current rate Thailand’s population will halve in about 50 years time.

I didn’t expect to see some of the districts near Bangkok being over 10% Muslim. Is this due to internal migration from the southern Muslim/Malay regions or are there other Muslim communities in Thailand??