I am planning a motorbike ride form Chiangmai to Hua Hin; but I do not want to go by the major highways. Provincial roads good. Any suggestions form those who might have done this already??
Officially Thailand have highways of 4 different classifications (white signs) and rural roads (blue signs)
So thus its a bit unclear to me what you mean by provincial roads, and what you want to ride and what roads you want to avoid?
Is 2 digit number roads too big? Is 3 digit road numbers too big? Etc etc…
But an example could be to start with R106 out of Chiang Mai and continue through Lamphun, Lampang and into Tak province. Then when R106 meets R101 you ride that further through Tak province into Kampaeng Phet province, then R1084 to Nakhon Sawan, then the ring road around Nakhon Sawan, then some minor roads to reach R333, continue on this through Suphan Buri, further into R321 to Nakhon Pathom. After that I guess you either have to find many smaller roads or just follow the main road R4 south to HH.
You could also ride R108 from Chiang Mai to Mae Sariang, then R105 towards Mae Sot, then R1175 down to R1, a little on R1 to R12 then R101 and same as above.
Even more adventurous is
R108 to R1099 Omkoi, then rural R3054 from Mae Tuen to Mae Ramat, then R1175 and same as above.
When riding south and around Bangkok I usually take R333 and R321 through Suphan Buri and even though some parts of this road has been quite heavy trafficed I found it much better than riding closer to Bangkok