Hi Patricia, thanks for your question 
I’ve always found that the English speaking markets of North America, UK, Australia, etc. + the Nordic countries are the easiest markets for selling SaaS into, at least in the early days. There’s a solid culture of trying out new online products, signing up for stuff and buying with a credit card.
Countries like France, Germany, Spain, etc. are all great markets, though the more you can localise the experience in terms of the language (product, sales, support, etc) the better you will do.
With regards to Asia, it’s all quite different, for example I don’t believe any foreign SaaS company has really had significant success in China. Japan is a great market, but you need to play a long game and make the up-front investment to build the local team and market on the ground (Korea is similar, but as Japan is larger most foreign companies focus there first). Both Salesforce and Zendesk have had a lot of success and built solid businesses in Japan, but it’s something that requires consistent effort over several years before things start to get really rolling.
I personally found that that India, Hong Kong, Singapore + the large markets of SE Asia (Malaysia, Thailand, Philippines, Indonesia, Vietnam) together make for the easiest entry point into Asia. As the way of doing business in those countries is culturally not too different to the West and English is widely spoken among executives at businesses likely to be buying a SaaS solution.