If they hold certain visa types. Have a look on the VFS website - it has the info. A lot of visas are outsourced to VFS these days. UK is and quite a few others
Some visas you can only apply in your home country or where you have long term visa/residency ie a Burmese could not apply for a Schengen Visa while in Thailand on a tourist visa - in face most non-Thais could not.
I see reading comprehension is once again beyond your ken! We are discussing the ability to even apply for a visa on particular visa types. Not the qualifying criteria FFS
I am not saying that. I am saying whether they can actually apply in Thailand on that visa. For example you need to be "Resident" in Thailand to apply for the Schengen here.
I think it depends on the particular country and visa. I saw a post someone applied for UK Visa on DTV and got it. I may be wrong but I think Schengen could not. Check through the posts in the group