With the thaievisa.go.th website in the section to upload supporting documents does it allow multiple documents to be uploaded in answer to one question.

 

I have 2 air tickets with different airlines one flying in one flying out.

I can upload one ticket on the website and see a small image of it to show its accepted. If I press the yellow button  to upload another document to the same question it shows that document is accepted.

 

Are both documents in the system or has the second replaced the first?

E-Visa did not when I applied in mid-January.  Best thing is to combine them into a single document.  Then upload it.  

Not possible. Once you upload a second document, the original one is replaced.

 

Among other things, I was requested to upload 12 months travel history.. not sure how to do that in a single jpeg file with size limts..?

That would require some serious skills.

 

What eventually happened was i uploaded only the front page of my passport and the application was approved.