The road shots look like R1155 again, near the Phu Chi Fa turn off.
In an earlier report I think you (& a few others) posted pics of a monument to villagers killed building the road.
This whole area from Chiang Khong - Thoeng - Chiang Kham has a fascinating history of battles with the communists in the (late 60s? &) early 70s.
R1155 & R1093 along the border were built in once communist controlled areas in the early 70s.
Pha Tang was a KMT base that used to supply arms & soldiers to help fight the communists in Laos.
Pratu Siam was literally a door into Laos through which supplies & soldiers went to fight in Laos.
In 1972 using KMT soldiers from Doi Mae Salong & Pha Tang the Thai govt tried to clean out the communists still controlling large areas of mountainous land around Doi Pha Mo & Doi Yao mountain ranges, south from Phu Chi Fah towards Chiang Kham & Thoeng. It did not succeed very well despite using artillery, police helicopters & air force gunships, only food & abandoned camps were captured & the govt forces suffered 8 dead & 42 wounded.
In December 1972 600 KMT soldiers were used in another attempt to sweep clean the Chiang Khong -Thoeng border areas. This also failed & saw 40 govt-KMT casualties from mines & booby traps & no enemy dead.
In April 1973 another attempt was made to clean out the area. This time 800 KMT - govt troops were used, including support from air force with helicopters & bombing runs from planes. They again failed to dislodge the communists. The govt side suffered 20 dead & 60 wounded.
That the roads were finally built is quite an achievement, for as they were being built they were often under fire from die hard communists. Many of the roads run along the ridgeline, because this is where you were not shot at from - above. If you were down in the valley the communists in the hills higher up could easily shoot down at you. And this is a reason why you often find amazing roads in the border areas of north Thailand. To successfully build a road through the communist controlled area you had to get up above them, so bulldoze a road straight up a spur & then & run along the ridge line where you could not get shot at,, except from down below. A lot of these roads are in also in Nan, especially R1081 on the Laos border side of Doi Phukha.
KMT soldiers were often used to guard & provide protection for the road contractors in building these roads in the border areas were communists once held sway.
Many, if not all the Hmong villages along R1093 are govt resettlement villages, where they settled the Hmong who came from Laos after the communists "won the war." They Hmong were put here to guard against future communist threats.