Short answers, pulled from the story.
According to Pew Research Center's 2020 data, there are approximately 324,190,000 Buddhists worldwide, representing about 4.1 percent of the global population. The ten countries with the largest Buddhist populations together account for over 91 percent of that total.
Buddhism is the state religion in four countries: Cambodia, Myanmar, Bhutan, and Sri Lanka. All four have large Buddhist majorities, with Cambodia at 96.9 percent, Myanmar at 89.9 percent, Bhutan at 74.7 percent, and Sri Lanka at 69.3 percent.
Thailand has the largest Buddhist population according to 2020 Pew Research Center figures, with approximately 67,620,000 Buddhists representing 94.4 percent of its population and about 20.9 percent of all Buddhists worldwide.
Mahayana is the largest branch, followed by around 53 percent of Buddhists and centered mainly in East Asia. Theravada is the second-largest branch at about 36 percent, concentrated in Mainland Southeast Asia and Sri Lanka. Smaller schools such as Navayana are followed scantily in India.
Pew Research Center identified Buddhism as the only major religion to have declined in its 2010 to 2020 global religious landscape report. Every other major religion tracked in that study showed growth during the same period.
The Asia-Pacific region is by far the center of global Buddhism, with an estimated 481,290,000 Buddhists representing 11.9 percent of the regional population as of 2010. All other regions fall well below 2 percent, with Europe at 0.2 percent and North America at 1.1 percent.