Neil Bennett I have loads of pdf-files (mostly 2 pages) in my Onedrive. Most of them are below 550kb, just one is larger than 1Mb = 1.08Mb. Text-files are "normally" never very large.
Just go to the Thai embassy or consulate's website back home and check out how to apply for a 60 days tourist visa. You can then extend the stay another 30 days at the local immigration office. Cost: ฿1.900. This is the easiest way to get 90 days.