Is it safe to file paper tax return on thermal paper?

[big toes]

Is it safe to print tax returns on A4 thermal paper with a thermal printer for filing?

I'm wondering if the pages could get smudged or marked by heat sources during transport through international mail, and become unreadable. 

I've been filing paper tax returns because of attachments and certain forms from abroad that can't be e-filed.  Next year I'm considering becoming itinerant without a fixed home abroad, and don't want to print tax returns at public printers to prevent having to share the documents with the salesperson or leaving behind copies on the printer/computer memory.

I was thinking of getting a cheap secondhand thermal printer, the type made for mobile office workers or van drivers, which is lightweight at only 0.5kg, and very compact around the size of a laser toner cartridge, but has to be fed thermal paper one sheet at a time. Other types of printers such as inkjets are more than 2-3 times heavier.

[Mike9241]

thermal paper is probably a poor choice. the mailed return could become so unreadable when it gets to the IRS that it would even know where to send a notice to report the failed filing.  other issues are your signature and dating