i think thugs will keep showing up until day 20 or even later, i play expert and i saw thugs a lot at early stage, the thievery mission with payment of 400 crowns or below will always leads you to around 7 – 10 thugs.
of course if you are not lucky, you will meet a fort with 5 well equip raiders inhabit in your very first mission after dear old Hoggert, but you could just simply abandon that mission, and go travel to other area of the map. sometimes i met mega ghoul in 1 skull beast hunting mission, but it means nothing other than bad luck.
also, the new patch gives us a progressing friendly combination of bandits, means you will find some bandit crews with very few raiders, which helps you to upgrade your gear even easier. i met a lot bandits group with 7 thugs and only 1 raider, they still looks like a pure raider set, but if you use your mouse hover over them, haha! surprise! they suddenly turn out to be the perfect farming targets at the moment.