Crocothemis servilia is an extremely widespread species, occurring throughout mainland tropical and subtropical Asia, Japan, the Greater and Lesser Sunda islands, the Philippines and Sulawesi. In the west it extends into the Levant and part of the Arabian Peninsula, Iraq, Iran, Armenia and Turkey. It has apparently been accidentally introduced [well done again, mankind] into Hawaii and the Caribbean, where it now occurs in Florida, Cuba, Jamaica and Puerto Rico.
We certainly did find this red dragonfly to be quite common in SE Asia, where we found it both in Cambodia and almost everywhere in Singapore where the regional book, A Photographic Guide to the Dragonflies of Singapore, gives it the vernacular name of Common Scarlet. I think I prefer the term Oriental Scarlet which is the name used by Dijkstra/Lewington, which includes it because of its being recorded on the Mediterranean coast of Turkey. Not having visited Turkey, we haven’t seen it there.
We have also seen one example, albeit dead and not at all scarlet, in Kowloon Park when visiting Hong Kong bound for the Antipodes in 2017. In 2019 we saw it on our visit to Sri Lanka.