I went through the trouble of getting vaccinated and getting the certificate for an RTW trip that included Brazil and Colombia.
After Colombia I went to Canada, Caribbean, Europe, South Korea and finally Hong Kong and back into Thailand.
You know what, nobody ever asked to see the thing.
Some countries have the immigration form that asks you "have you been to a farm in the last x days / have you been to south America in the last x days" / "name all the countries you have visited in the last x days". I always truthfully put Brazil and Colombia in there. Nobody ever asked to see my Yellow Fever cert.
Thailand doesn't even ask what you have been up to. They just want to know your last port of embarkation which can't be any port in Argentina as there are no direct flights.
Based on all this I would say you can carry your doctor's waiver just in case but don't expect any hassles.