What is the time frame for uploading additional documents after applying for a visa in Thailand?

14 days. If you need more time I would upload a document explaining why. Otherwise I'm afraid your application may be automatically canceled if you don't do anything.

I'm quite sure I see somewhere on the website that said after 14 days applications would be deleted. However, my girlfriend had attempted to apply via UK Embassy on our trip there to see if it would work without being a UK resident. Unfortunately, she was not able to due to requested docs, one of which being to prove you are a UK resident.

This was back around August 29th, so over 1 month ago and when I check the account she is still able to upload documents even now on the 8th October. So you may be fine but honestly, there's no saying exactly how their system works internally and if it changes from embassy to embassy in different locations.

Just try to get the doc as soon as possible.