Having freelanced myself in South America I could give you a sound advice BUT you would first need to answer some questions.
1) How long do you plan on being in South America? At the end of 2017 will you be back in Ireland or still being in South America? In other words was is your country of residence for tax purposes on Dec. 31 2017 ? That is the key element to consider. Link
2) In latin America you can freelance with a legal working permit BUT in all these countries more than 50% of the economy is under the table. In all these countries expatriate work under the table. The question you need to answer is then: Who will be your employer, a company or the owner of this company? Working undeclared in Latin America is very common, what are the risks? The legal risks depend on the country and their laws. In which country will you travel? How long will you stay there? You will have a tourist visa or a working visa?
3) An important detail, your health. Check how long you can be out of Ireland without loosing your social health benefits in Ireland? In my country, if I am abroad for more than 180 days, I loose my national health coverage. Evaluate the amount of days you will be out of Ireland and where you want to be on Dec. 31th. That could change a lot of things in your life.